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USMLE: step 1 > Behavioral / Stats > Flashcards

Behavioral / Stats Flashcards

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USMLE® Step 1 flashcards
1
Q

What is a cross sectional study?

A
  • Purely observational
  • Asks, what is going on at this point in time
  • Snap shot of exposures and outcomes simultaneously
  • Shows risk association with disease
    DOES NOT ESTABLISH CAUSALITY
    *Disease prevalence is characteristic measure
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2
Q

What CAN’T a cross sectional study establish?

A

Causality

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3
Q

What is disease prevalence characteristic measure of?

A

Cross sectional study

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4
Q

What is prevalence?

A

Portion of people in population with disease at any given time

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5
Q

Weakness of cross sectional study?

A

Shows correlation, but DOES NOT prove causation

*For example, maybe there is another factor that is causing both the disease and the risk factor you are studying

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6
Q

What is a case control study?

A 
Observation and RETROSPECTIVE study asking, "what happened?"
Case: subjects with disease
Control: subjects without disease 
- Previous exposure is being analyzed 
*Metric is the odds ratio
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7
Q

What is the odds ratio the metric in?

A

Case control study

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8
Q

What is odds ratio?

A
  • Odds of exposure to risk factor in case (disease) : odds in control (healthy)
  • **Does exposure increase odds you have disease
  • Used in case control study measuring:
  • ***If odds ratio is 9, you’re 9 times more likely to develop disease if you had exposure
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9
Q

Define odds?

A

Odds = P / (1 - P)

  • P = probability event happening
  • 1 - P = probability not happening
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10
Q

What is a cohort study?

A

Observational prospective study
“Does exposure increase risk of disease?”
- If high cholesterol, will you have higher risk of MI
*Relative risk is characteristic measure
- Focusing on if risk is causing disease

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11
Q

What study uses related risk?

A

Cohort study

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12
Q

What is relative risk?

A

P1/P2
P1 = risk of disease if exposed
P2 = risk of disease is unexposed

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13
Q

What makes a clinical trial high quality?

A
  1. Randomization
  2. Controlled
  3. At least double blind
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14
Q

What is single, double, triple single?

A

Single: patient doesn’t know if getting treatment
Double: Neither doctor or patient know who got drug
Triple: same as above but researcher also does not know

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15
Q

What is phase 1 study?

A
  • Drug studied in 10 - 20 healthy volunteers

- Assess safety, toxicity, kinetics

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16
Q

What is phase 2 study?

A
  • 100s of people WITH disease to assess efficacy
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17
Q

What is phase III study?

A
  • 1000s of people with disease

- Treatment assessed vs. placebo or best available treatment

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18
Q

Trick to remember # of people in phases of study?

A

The number of the phase, corresponds to number of zeros in patients studied

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19
Q

What is phase IV?

A
  • All people on drug post release to assess rare or LT effects
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20
Q

Questions being asked in 4 phases?

A
  1. Is it safe
  2. Does it work
  3. Is it more effective
  4. Can we keep on using it
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21
Q

When drawing 4x4 box what is on left side and top of it?

A

Left: test
Top: disease
***Just read it left to right, “we are testing for disease”
Test comes before disease as it does on chart

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22
Q

Define sensitivity?

A

Ability to detect disease when it is actually present

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23
Q

Equation for sensitivity?

A

TP / (TP + FN)

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24
Q

What are high sensitivity tests good for?

A 
"SNOUT"
SN = sensitivity
Out = ruling out 
Ruling things out
***This is true because high value is approaching one with means false negative = zero
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25
Q

Define specificity?

A
  • Ability to indicate non disease when disease is not present
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26
Q

Equation for specificity?

A

TN / (TN + FP)

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27
Q

What are tests with high specificity good for?

A

“SPin”
SP = Specificity
IN = Ruling in a disease
*As value approaches 1 it will have very few false positives
*Good for confirmatory test after positive screening

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28
Q

Equation for positive predictive value?

A

TP / (TP + FP )

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29
Q

Equation for negative predictive value?

A

TN ( TN + FN )

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30
Q

Which values vary with prevalence of disease?

A

PPV and NPV

*Sensitivity / specificity DO NOT

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31
Q

Impact of high prevalence of disease on measurements?

A

Higher PPV, lower NPV

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32
Q

Difference between prevalence and incidence?

A

Prevalence includes old cases where incidence does not

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33
Q

How does the 4 x 4 chart switch when using it for odd ratio?

A

Exposure is on left, disease is on top:

  • Makes sense in reading left to right as you must first be exposed to get the disease
  • *Then layer in A, B, C, D alphabetically as if you were reading
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34
Q

What is the odds ratio equation?

A

( AD ) / ( BC )

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35
Q

Does odds ratio imply causation?

A

No, only correlation

- Remember there could be another factor causing both the risk factor and the disease

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36
Q

Relative risk equation?

A

( A / [A + B] ) / ( C / [C+D] )

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37
Q

Relative risk reduction equation?

A

1 - RR

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38
Q

What is attributable risk?

A

Difference in risk between exposed and unexposed group?

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39
Q

Attributable risk equation?

A

(A/ [A+ B] ) - ( C / {C+D} )

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40
Q

What is absolute risk reduction?

A

Difference in risk attributable to intervention

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41
Q

Equation for absolute risk reduction?

A

( C / {C+D} ) - (A/ [A+ B] )

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42
Q

What is number needed to treat?

A

Number of patients needed to be treated for 1 patient to benefit

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43
Q

Equation for number needed to treat?

A

1 / ARR (Absolute risk reduction)

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44
Q

What is number needed to harm?

A

Number of patients needed to be exposed to risk factor for 1 patient to be harmed?

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45
Q

Equation for number needed to harm?

A

1 / AR

- Think AR = AR assault rifle

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46
Q

What is precision?

A

Consistency and reproducibility of a test

***AKA reliability

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47
Q

Another name for reliability of test?

A

Precision

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48
Q

What is accuracy? Another name for accuracy?

A

How close test measures are to true values

- AKA: validity

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49
Q

Another name for validity?

A

Accuracy

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50
Q

What does random error do?

A

Decreases precision and reproducibility of test

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51
Q

What is systematic error?

A

Reduces accuracy by consistently skewing results in a particular direction

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52
Q

What is bias?

A

1 result / outcome is systematically favored over another

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53
Q

What is berkson’s bias?

A

Only people from hospital were selected for study: form of selection bias as they are not as healthy as the general population
- Same idea occuring if you select people healthier than normal

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54
Q

What type of bias is it if certain type of people drop out of study?

A

Selection

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55
Q

What is procedure bias?

A

Subjects in different groups are not treated the same

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56
Q

What is lead time bias?

A

Detecting disease early being confused with better survival

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57
Q

What is the median?

A

Middle number in set when organized numerically

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58
Q

Measurement most affected by outliers? Least?

A

Most: Mean
Least: Mode

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59
Q

How is median calculated with even list of numbers?

A

Average of middle two numbers

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60
Q

What happens to SD in very precise test?

A

It is decreased

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61
Q

%s falling in first 3 standard deviations?

A

1st: 68
2nd: 95
3rd: 99.7

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62
Q

Equation for standard error of mean?

A

Standard deviation / (Square root sample size)

* As sample size increase, SEM decreases

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63
Q

Does standard deviation impact sample size?

A

No, only impact standard error of mean

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64
Q

Break out of measurements in positive /negative skewed distribution?

A

Positive: Mode Median > Mean

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65
Q

Best number in skewed distribution?

A

Median

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66
Q

What is the null hypothesis?

A

That there is no statistical difference between 2 groups

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67
Q

What is on 4 x 4 box in hypothesis testing?

A

Results on left, population on top

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68
Q

What is type I error?

A

Stating there is an effect/difference when one does not actually exist

  • Null rejected, experimental accidently accepted
  • This is in box B
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69
Q

What is alpha?

A

The probability of making type I error (Study says there is a difference when in reality there is not)

70
Q

How to interpret P value?

A

If P

71
Q

What is type II error?

A

“Box C”

  • Saying there is not a difference when there really is one
  • You fail to reject null hypothesis when in reality it is false
72
Q

What is beta?

A

Probability of making type II error

73
Q

Ways to reduce Type II error?

A
  1. Increase sample size
74
Q

2 things decreased by increasing sample size?

A
  1. Type 2 error

2. Standard error of mean

75
Q

Which error is false negative / positive?

A

Type I: False positive

Type II: False negative

76
Q

What is power?

A

Likelihood you find a difference when one truly exists

- Probability of rejecting null hypothesis when it is false

77
Q

What is a powerful study?

A

High likelihood of finding a difference if one is present

78
Q

Equation for power?

A

1 - Beta (this is type II error )

79
Q

What impacts power?

A
  1. Samples size increases: power in numbers
  2. Decreased standard deviation
  3. Increased alpha
  4. Increased mean value between groups
80
Q

What is confidence interval?

A

Range of values in which specified sample means is expected to fall

81
Q

What does 95% confidence interval correspond to?

A

P value of .05

82
Q

What is Z score at 95% / 99%confidence interval?

A

95%: 1.96

99%: 2.58

83
Q

3 rules for interpreting confidence intervals?

A
  1. If 95% confidence interval for mean difference between 2 variables includes zero, then there is no significant difference and should not reject null hypothesis
  2. If 95% interval for odds ratio or relative risk includes 1, null hypothesis should not be rejected
  3. If CI between 2 groups overlap, they are note significantly different
84
Q

What does a T test do?

A

Compares mean of 2 groups to see if there is statistical difference

85
Q

What is Anova test?

A
  • Compares means of > 3 groups to see if statistical difference
  • Same as T, just for more groups
86
Q

What is Chi square test?

A
  • Comares 2 or more percentages or proportions of categorical outcomes
  • EG: comparing % of smokers with lung cancer to % smokers without lung cancer
87
Q

What is correlation coefficient?

A
  • 1
88
Q

What is coefficient of determination?

A

R Squared

89
Q

What is autonomy?

A

Respect patient as individuals and honor their preferences in medical care or refusing care

90
Q

What can refuse treatment?

A

Any competent person > 18 at any time

91
Q

Does autonomy or beneficence trump?

A

Autonomy

92
Q

3 conditions of informed consent?

A
  1. Disclosure: discussion with patient
  2. Capacity and understanding to agree to plan
  3. Acting voluntarily / free from coercion
93
Q

Exceptions to informed consent?

A
  1. Patient lacks capacity: act in beneficence
  2. Medical emergency: implied consent
  3. Therapeutic privilege: withholding info if it would damage outcome
    - EG: not telling suicidal patient they have cancer
94
Q

How can minor be emancipated?

A
  1. Married
  2. Have a child
  3. Self supporting
  4. Joined military
95
Q

When is parental consent not required?

A
  1. Emergency care
  2. Contraceptives
  3. STDs
  4. Management of addiction
96
Q

When is parent not allowed to refuse treatment for child?

A

Life and death situation

97
Q

Components of decision making capacity?

A
  1. Make and communicate choice
  2. Fully informed
  3. Stable decision over time
  4. Consistency with their values and goals
  5. No delusions or hallucinations
  6. > 18 yo or emancipated
98
Q

Do intoxicated people have capacity?

A

No

99
Q

What is a living will?

A

Written description of treatments if patient becomes incapacitated

100
Q

What is the order of surrogate decision making?

A
  1. Spouse
  2. Adult children
  3. Parents
  4. Siblings
101
Q

When is confidentiality waived?

A
  1. Harm to self / others
  2. No way to warn / protect people at risk
    3.
102
Q

When should you go to superior, court, or ethics committee?

A

This is almost never the answer

103
Q

When should you refer patient to another physician?

A

never

104
Q

What to do in non adherence?

A

Find out why and determine willingness to change behavior

105
Q

What to do if patient continues to smoke?

A

Ask how they feel about smoking then offer advice if they express desire to quit

106
Q

Response if trouble taking medicines?

A
  • Give written instruction and try to simplify regimen
107
Q

What to do if family asks for information?

A

Avoid this unless explicit permission is given from patient

108
Q

What to do if child wants to know about illness?

A

Ask parents first what they have told child

109
Q

What to do if pregnant minor?

A
  1. DO NOT advise abortion
  2. Advise to talk to parents
  3. Mother retains right to make decisions about fetus
110
Q

What to if family wants adoption on child wants to keep baby?

A
  • Provide her with information about caring for child

- Encourage open dialogue with parents

111
Q

What to do if patient asks for suicide??

A

Refuse involvement and give appropriate analgesic

- Medically appropriate analgesics can be given even if it will shorten life

112
Q

What to do if suicidal?

A

Suggest they remain in hospital voluntarily

113
Q

When can suicidal person be withheld in hospital against will?

A
  • They refuse to be admitted

- You deem them to lack capacity

114
Q

If patient gets romantic?

A
  1. Never
  2. Ask for chaperone
  3. Don’t say not while they’re a patient
  4. Ask direct, close ended questions
115
Q

What to do if patient says they feel ugly?

A
  1. Ask why they feel this way

2. Do not provide reassurance

116
Q

What to do with angry patient?

A
  1. Acknowledge anger without taking personally
  2. Do not make excuses
  3. Encourage open communication with old physicians
  4. Apologize but dont try to explain it
117
Q

What if patient is upset about how other doctor treated them?

A

Encourage them to speak directly with doctor

118
Q

What if patient has problem with office staff?

A

Tell patient you will speak to that person personally

119
Q

What to do if medical error is made?

A

Always inform patient

120
Q

When does moro disappear?

A

3 months

121
Q

When does rooting disappear?

A

4 months

122
Q

When does palmar disappear?

A

6 months

123
Q

When does babinski disappear?

A

12 months

124
Q

When can baby lift head?

A

1 month

125
Q

When can baby roll and sit?

A

6 months

126
Q

When can you crawl?

A

8 months

127
Q

When can you pincer?

A

10 months = 10 fingers for ten hands

128
Q

When can you stand?

A

10 months = on all 10 toes

129
Q

When can you walk?

A

12 - 18 months

130
Q

When can you smile?

A

2 months

131
Q

Stranger and separation anxiety?

A

Stranger: 6 months
Separation: 9 months

132
Q

Orient to voice / name?

A

Voice: 4 months
Name: 9 months

133
Q

Object permanence?

A

9 months

134
Q

Mama and dada?

A

10 months

135
Q

When can you say single words?

A

1 year

136
Q

Parallel play?

A

12 months

137
Q

Rapprochement?

A

24 months

138
Q

Cooperative play?

A

36 months

139
Q

Core gender identity?

A

36 months

140
Q

Imaginary friends?

A

48 months

141
Q

Kick a ball?

A

24 months

142
Q

200 word vocab / 2 word phrases?

A

24 months

143
Q

Tricycle?

A

3 years

144
Q

1000 word vocab?

A

3 years: think, 1 year for each zero

145
Q

Detailed stories?

A

48 months

146
Q

How many cubes can a kid stack?

A

Age in years x 3

147
Q

When can you complete simple shape?

A

3 years

148
Q

Does sexual interest decline in age?

A

Not in men: decreased libido in women post menopause

149
Q

Sleep changes in aging?

A
  1. Decrease REM
  2. Decrease slow wave
  3. Increased awakening
  4. Increased latency
150
Q

Age group with highest suicide rate?

A

65 - 74

151
Q

Fat change in old age?

A

Brown: decreases
White: increases

152
Q

3 stages of disease prevention?

A

Prevent
Screen
Treat

153
Q

What to say if stem says “offer them specific drug because they have medicaid?”

A

Dont do it! Offer them best and all treatment options regardless of insurance

154
Q

What gets medicare?

A
  1. > 65

2.

155
Q

4 parts of medicare

A

Part A: Admissions to hospital
Part B: Basic bills
Part C: Combined (A + B by private company)
Part D: Drugs

156
Q

What is medicaid?

A

Insurance for Destitute

157
Q

When can you point?

A

12 months

158
Q

Climb stairs?

A

18 months

159
Q

Feed self with fork?

A

20 months

160
Q

When can you copy line, circle, etc?

A

4 years

161
Q

Hop on one foot?

A

4 years

162
Q

Use button / zipper?

A

5 years

163
Q

Greatest killers

A
  1. Congenital defects

2.

164
Q

Greatest killers > 65?

A
  1. Heart disease

2. Cancer

165
Q

Age group with greatest cancer death?

A

45 - 60 yo

166
Q

Who is cancer second leading cause of death for?

A

1 - 14
35 - 44
> 65

167
Q

Greatest killer across all groups?

A

Unintentional injury

168
Q

When does hospital visit count as readmission?

A

Within 30 days of first visit and does not have to be for readmission

169
Q

What is human factors design?

A

Limiting human error by developing systems that simplify and standardize protocol

170
Q

What is the PDSA cycle?

A

Plan
Do
Study / analyze
Act

171
Q

Example of balancing measurement?

A

How do HBA1C levels correlate with disease

172
Q

Example of process measurement?

A

Performance of system: % of patients with HBA1C measurement in 6 months

USMLE: step 1 (15 decks)

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