Introductory Statistics Flashcards

1
Q

null hypothesis

A

prediction that the observed difference is due to chance alone and not due to a systematic cause

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2
Q

null hypothesis is the statement of

A

no difference

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3
Q

statistics provide the evidence to

A

reject or fail to reject the null

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4
Q

alternative hypothesis

A

prediction that some observed difference is significant and due to some knowable cause

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5
Q

alternative hypothesis is the statement that

A

there is a difference between groups not attributable to chance alone

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6
Q

what does statistic testing test?

A

the likelihood of differences occurring by chance alone

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7
Q

p level

A

the predetermined probability researcher is willing to make a type 1 error

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8
Q

p level is also referred to as the

A

alpha level

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9
Q

p

A

“Only 5% of the time, this difference will be observed due to chance alone”

5% chance observed difference was due to chance
95% confident that results were due to independent variable(s)

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10
Q

p<0.001

A

.1% chance observed difference was due to chance

99.9% confident that results were due to independent variable(s)

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11
Q

nominal

A

label or category without rank

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12
Q

ordinal

A

label or category with some meaningful order or sequence

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13
Q

interval

A

scaled measure with an arbitrary zero point

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14
Q

ratio

A

scaled measure with an absolute zero point

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15
Q

inferential statistics don’ts (3)

A

◦Prove cause and effect
◦Estimate clinical effectiveness
◦Estimate risk/benefit

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16
Q

inferential statistics do’s (2)

A

◦Estimate the probability of getting results due to chance

◦Suggest numerical differences

17
Q

Statistical significance (p-value) indicates

A

difference between two groups

18
Q

Effect size describes the

A

magnitude of difference

◦How much more effective?

19
Q

We can standardize difference and compare it to

20
Q

effect size

A

standard measure, can be calculated from various statistical outputs

21
Q

Standardized mean effect, expresses the mean difference between

A

two groups in standard deviation units (Cohen’s d)

◦Need mean and standard deviation for each group

22
Q

values for effect size range from

A

-3 to 3

same as standard dev

23
Q

standard interpretation of effect size
.8=
.5=
.2=

A
◦.8 = large (8/10 of a standard deviation unit)
◦.5 = moderate (1/2 of a standard deviation)
◦.2 = small (1/5 of a standard deviation)
24
Q

relative risk

A

A measure of risk based on a comparison of disease (or other health outcome) incidence in two distinct groups

25
what is relative risk the ratio of?
the probability of the event occurring in the exposed group versus a non-exposed group
26
odds ratio
Comparing the odds of an event in one group to the odds of an event in some comparison group
27
odds ratio estimates
association
28
Both the odds ratio and relative risk compare the
likelihood of an event occurring between two distinct groups
29
are relative risk or odds ratio easier to interpret?
RR is easier to interpret and consistent with the general intuition◦comparison between subgroup and entire population, rather than subgroup and remainder of population
30
Case-control designs limit
RR calculation | cases selected on basis of disease rather than exposure (RR compares exposed to unexposed)
31
OR and RR are comparable when the disease studied is
rare
32
OR overestimates RR, when the disease is more
ccommon | ◦should be avoided if RR can be used
33
sensitivity vs specificity
Sensitivity is the proportion of patients with the disease who test positive Specificity is the proportion of patients withoutthe disease who test negative
34
confidence interval tells you
the most likely range of the unknown population average
35
what three things impact the width of a confidence interval
◦Confidence level: typically 95% ◦Variability: standard deviation ◦Sample Size: Smaller sample sizes generate wider intervals