Introductory Statistics

Question 1

null hypothesis

Answer 1

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

Question 2

null hypothesis is the statement of

Answer 2

no difference

Question 3

statistics provide the evidence to

Answer 3

reject or fail to reject the null

Question 4

alternative hypothesis

Answer 4

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

Question 5

alternative hypothesis is the statement that

Answer 5

there is a difference between groups not attributable to chance alone

Question 6

what does statistic testing test?

Answer 6

the likelihood of differences occurring by chance alone

Question 7

p level

Answer 7

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

Question 8

p level is also referred to as the

Answer 8

alpha level

Question 9

p

Answer 9

“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)

Question 10

p<0.001

Answer 10

.1% chance observed difference was due to chance

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

Question 11

nominal

Answer 11

label or category without rank

Question 12

ordinal

Answer 12

label or category with some meaningful order or sequence

Question 13

interval

Answer 13

scaled measure with an arbitrary zero point

Question 14

ratio

Answer 14

scaled measure with an absolute zero point

Question 15

inferential statistics don’ts (3)

Answer 15

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

Question 16

inferential statistics do’s (2)

Answer 16

◦Estimate the probability of getting results due to chance

◦Suggest numerical differences

Question 17

Statistical significance (p-value) indicates

Answer 17

difference between two groups

Question 18

Effect size describes the

Answer 18

magnitude of difference

◦How much more effective?

Question 19

We can standardize difference and compare it to

Answer 19

0

Question 20

effect size

Answer 20

standard measure, can be calculated from various statistical outputs

Question 21

Standardized mean effect, expresses the mean difference between

Answer 21

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

◦Need mean and standard deviation for each group

Question 22

values for effect size range from

Answer 22

-3 to 3

same as standard dev

Question 23

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

Answer 23

◦.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)

Question 24

relative risk

Answer 24

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

Question 25

what is relative risk the ratio of?

Answer 25

the probability of the event occurring in the exposed group versus a non-exposed group

Question 26

odds ratio

Answer 26

Comparing the odds of an event in one group to the odds of an event in some comparison group

Question 27

odds ratio estimates

Answer 27

association

Question 28

Both the odds ratio and relative risk compare the

Answer 28

likelihood of an event occurring between two distinct groups

Question 29

are relative risk or odds ratio easier to interpret?

Answer 29

RR is easier to interpret and consistent with the general intuition◦comparison between subgroup and entire population, rather than subgroup and remainder of population

Question 30

Case-control designs limit

Answer 30

RR calculation

cases selected on basis of disease rather than exposure (RR compares exposed to unexposed)

Question 31

OR and RR are comparable when the disease studied is

Answer 31

rare

Question 32

OR overestimates RR, when the disease is more

Answer 32

ccommon

◦should be avoided if RR can be used

Question 33

sensitivity vs specificity

Answer 33

Sensitivity is the proportion of patients with the disease who test positive

Specificity is the proportion of patients withoutthe disease who test negative

Question 34

confidence interval tells you

Answer 34

the most likely range of the unknown population average

Question 35

what three things impact the width of a confidence interval

Answer 35

◦Confidence level: typically 95%
◦Variability: standard deviation
◦Sample Size: Smaller sample sizes generate wider intervals