Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Behavioral Health: Week 1 > Beehler: Biostats > Flashcards

Beehler: Biostats Flashcards

1
Q

What is the frequency/spread of a disease in a population?

A

prevalence
incidence
attack rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How well does a test differentiate sick from healthy people?

A

sensitivity
specificity

*refers to test VALIDITY, how good is this test at comparing those two groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Of those in a population who test as sick or healthy, how many are truly sick or healthy?

A

Predictive value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the impact of a medicine/treatment?

A

risk reduction/increase

number needed to treat/harm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What helps you to understand DISEASE BURDEN or the EXTENT of a health problem?

A

Prevalence (point prevalence)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Period prevalence

A

during a PERIOD of time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Lifetime prevalence

A

over the COURSE of a lifeteime

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the equation for prevalence?

A

Number of people with a disease at a specific point in time/ Number of people AT RISK for the illness at that point in time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A county in Minnesota has a population of 1,500. In 2013, 180 individuals were diagnosed with type 1 diabetes. Last year, 30 individuals were diagnosed with it. What is the PREVALENCE of type 1 diabetes in this population in 2014?

A

= (180+30)/1500
= 210/1500
= 0.14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What helps understand the RISK of a specific health event–the number of NEW cases?

A

Incidence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is cumulative incidence?

A

total number reported over time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the eqtn for incidence?

A

Number of NEW people with disease during a time period/ Number of people at risk for illness during that time period

*better for ACUTE cases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

A county in Minnesota has a population of 1,500. In 2013, 180 individuals were diagnosed with type 1 diabetes. Last year, 30 individuals were diagnosed with it. What was the INCIDENCE of type 1 diabetes in this population in 2014?

A

= 30/(1500-180)
= 30/1320
= 0.023

*180 from 2013 are removed b/c they’re no longer new cases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is attack rate?

A

Type of incidence used when nature of disease is acute & population observed for short period of time (e.g., outbreaks, specific exposures–flu, chicken pox, exposure)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the eqtn for attack rate?

A

Attack rate = # new cases / # exposed

*short period of time, confined area, exposure is impt (i.e. cholera in Haiti)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is secondary attack rate?

A

Secondary attack rate = # new cases / (# exposed – primary cases)

Measures person-to-person spread of disease after initial exposure

*take out ppl who were hit with the flu

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Within a kindergarten class, 5 of 35 kids develop chicken pox during a 1-week period. In the next two weeks another 10 kids also come down with chicken pox. What are the attack and secondary attack rates of chicken pox in the classroom?

A

Attack (whole time)
=(5+10)/35
= 15/35 = 0.43

Sec. Attack (second round)
= 10/(35-5)
= 10/30 = 0.33

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What affects prevalence and incidence?

A

Duration of illness (longer/chronic -> higher prevalence)

Number of new cases (more new cases -> higher prevalence) MORE PPL W/ DISEASE

Migration

  • In-migration (ill -> higher prevalence) SICK PPL MOVING IN
  • Out-migration (well -> higher prevalence) HLTHY PPL MOVING OUT
  • Recovery & death -> lower prevalence

Prevention -> lower incidence REDUCE NEW CASES

Changes in diagnostic criteria or reporting WHAT COUNTS AS SICK/HEALTHY CAN CHANGE (i.e. criteria for AIDS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the relationship between prevalence and incidence?

A

Prevalence = Incidence x (average) duration* (assumes incidence and duration are stable)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

When is prevalence higher than incidence?

A

disease is long term (diabetes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

When are prevalence and incidence the same?

A

illness is acute (flu)

22
Q

What is sensitivity? (test of validity)

SNOUT- negative don’t have it (True positives)
SPIN- positive, do have it (True negatvies)

A

The probability that a diseased person will be identified correctly by a diagnostic/screening test (AKA true-positive probability or true-positive rate)

23
Q

What are true positives vs false negatives?

A

ill identified as ill

ill identified as well

24
Q

What is the eqtn for sensitivity?

A

True positives/ Total # ill people [true positives + false negatives]

25
Q

Highly sensitive tests identify…

A

most or ALL sick people

26
Q

A group of individuals who were exposed to Lyme disease were screened using a new test developed for early detection. Of the 344 screened, the disease was confirmed in 258. The new test detected 263 cases of Lyme disease, 32 of which were disconfirmed. What is the sensitivity of the new test?

A

= True positives / total # ill = 231/258 = 0.90

90% who have Lyme will be correctly identified as having Lyme

27
Q

What is specificity?

NO N–> TRUE NEGATIVE

A

The probability that a well HEALTHY person will be identified correctly by a diagnostic/screening test (AKA true-negative probability)

28
Q

What is the diff between a true negative vs. a false positive?

A

true neg- well ppl identified as well

false pos- well people identified as ill

29
Q

What is eqtn for specificity?

A

= True negative/Total # well people [true negatives + false positives]

30
Q

What does it mean if you have a highly sensitive test?

A

High sensitivity -> err on the side of OVER DIAGNOSING

  • Identify MOST or ALL possible disease cases
  • Most useful when under-diagnosing may lead to severe consequences (e.g., fast developing cancers)
31
Q

What does it mean if you have a highly specific test?

A

High specificity -> err on the side of UNDER diagnosing

  • Identify most or all well people
  • Most useful when over-diagnosing may lead to dangerous, painful, or unnecessary treatment
32
Q

What happens if you lower the cutoff?

A

Err on the side of OVER diagnosing

33
Q

What is predictive value?

how does test work in my population

A

probability that a test will give the CORRECT dx

34
Q

What does predictive value depend on?

A

test sensitivity and specificity

prevalence of the disease in the pop being tested

**vary from pop to pop, study to study

35
Q

What is the eqtn for positive predictive value?

A

= True positives/All positives [true + false positives]

*the probability that someone who tests POS for the disease truly has it

= 231/263 = 0.88

36
Q

What is the eqtn for negative predictive value?

A

= True negatives/ All negatives [true + false negatives]

*probability that a person who tests NEG truly is healthy

= 54/81 = 0.67

37
Q

How does high disease prevalence affect predictive value?

A

Higher positive predictive value (i.e., greater chance that positive test result reflects true illness–SO MUCH DISEASE IN A POP)

Lower negative predictive value (i.e., lower chance that negative test result reflects disease-free status)

38
Q

How does lower disease prevalence affect predictive value?

A

Lower positive predictive value (i.e., lower chance that positive test result reflects true illness)

Higher negative predictive value (i.e., greater chance that negative test results reflects disease-free status)

39
Q

What is a randomized controlled trial?

A

Have at least one treatment group and one control group

People in both groups may respond positively (e.g., placebo effect) or negatively (e.g., harmful effects)

40
Q

What is the control event rate?

A

Proportion of control group participants who have a BAD outcome after “treatment” (e.g., placebo or no treatment)

41
Q

If 10 of 30 control group participants become sicker after a trial what is the CER?

A

CER = 10/30 = 0.33 = 33% had adverse outcomes

42
Q

What is the EER (experimental event rate)?

A

Proportion of treatment group participants who have a bad outcome after treatment (e.g., new drug)

43
Q

If 4 of 30 treatment group participants become sicker, what is the EER?

A

EER = 4/30 = 0.13 = 13% had adverse outcomes

44
Q

What is absolute risk?

A

probability of developing a disease or undesired outcome

*tells you whether there’s a reduction or increase as the result of a treatment

CER-EER or EER- CER

45
Q

What is ARR (risk difference)?

A

Control event rate is HIGHER than experimental event rate

CER – EER > 0

46
Q

What is ARI?

A

Control event rate is LOWER than experimental event rate

CER – EER < 0

47
Q

After participating in an RCT of a new cancer drug, 10 of 30 control group participants become sicker and 4 of 30 treatment group participants become sicker. Did the new treatment reduce or increase absolute risk? By how much?

A

CER – EER
= 10/30 – 4/30
= .33 - .13 = .20
= 20% REDUCTION

*As the result of this tx is risk increased or decreased

(relative= control vs. treatment)

48
Q

What is NNT?

A

Number of patients who need to be treated to get 1 additional patient a favorable outcome

NNT = 1/ARR

49
Q

What is NNH?

A

Number of patients who, if they were treated, would result in 1 additional patient being harmed

NNH = 1/ARI

50
Q

What is NNT is 5?

A

For every 5 people treated, 1 more person would respond to the drug

51
Q

What if NNH is 3?

A

If 3 were treated, 1 more person would not respond compared with the control group

52
Q

In a study,200 patients received a new drug to slow the progression of Parkinson’s and 300 patients did not receive the medication. 20 patients in the treatment group and 60 patients in the control group had a typical progression of Parkinson’s. What is the absolute risk reduction and number needed to treat?

A

CER- EER
60/300-20/200
= .2-.1= 10% REDUCTION

NNT= 1/.1 = 10

Behavioral Health: Week 1 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions