Pop/Hypothesis

Question 1

population

Answer 1

universe of things

Question 2

parameter

Answer 2

characteristic of population - almost always unobservable

Mean US household income

Question 3

sample

Answer 3

subset of population - cannot observe pop so collect sample

Question 4

Population: all with PD
Sample: ____

Answer 4

100 patients with PD who are seen at Banner over 5 year period

Question 5

parameter

Answer 5

characteristic of populatuon

Question 6

estimate of pop parameter

Answer 6

computed using data from sample we hope is near true value of parameter
statistic

Question 7

any computed measure from sample

Answer 7

statistic

Question 8

sample: 100 patients with PD who are seen at Banner over 5 year period
estimate: _____

Answer 8

32/100 have dementia

Question 9

law of large numbers

Answer 9

as sample size increases, we expect sample mean to be closer to true mean

Question 10

central limit theorem

Answer 10

as sample size increase sampling distribution of sample mean looks more and more bell shaped

Question 11

what does statistical significance of 0.05 mean

Answer 11

an observed result is regarded as statistically significant if it had a 5% or smaller likelihood of occurring simply due to chance

Question 12

type I error

Answer 12

rejecting null when null is true (FP)

alpha usually set to 0.05

Question 13

type II error

Answer 13

fail to reject null when null is false (FN)

beta

Question 14

hypothesis testing procedure

Answer 14

1) specify null and alternative
2) choose alpha, prob of making type I error (0.05)
3) compute some value from data (test statistic)
4) compute p value based on test statistic
5) if p value

Question 15

P value

Answer 15

probability of observing data as supportive or more supportive of the alternative hypothesis than the actual data

Question 16

two tailed test vs one tailed test example

Answer 16

two tailed H0: the blood pressure before treatment doesn’t equal blood pressure after treatment
one tailed H0: the blood pressure after treatment will decrease

differnece in medicines, or one medicine better than other

Question 17

why to use two-sided

Answer 17

conservative: if 2-sided significant then one sided will be too
prevents concerns that you may have chosen direction of alt hypothesis after seeing data

Question 18

causes of type I error

Answer 18

chance, inappropriate methods or assumptions about data

Question 19

cause of type 2 error

Answer 19

low statistical power

sample size too small

Question 20

power calculation

Answer 20

1-Beta (typeIIerror)

Question 21

avoiding type ii error

Answer 21

increase power by increasing sample size

Question 22

power depends on

Answer 22

sample size, size of true underlying effect, variability in measurements, chosen significance level and its sidedness, type of analysis

Question 23

decreasing sample size while maintaining statistical power

Answer 23

reduce number tx groups
find more precise measurement
decrease variability in measurements (make subjects more homogeneous, use stratification, average multiple measurements on each subject)

Question 24

properties of normal distribution

Answer 24

bell-shaped
mean = median = mode
symmetric
tails are asymptotic (never touch the x)

Question 25

standard normal distribution

Answer 25

mean 0 and standard deviation 1

Question 26

why is normal distribution important

Answer 26

lots of bio measurements normal approx

CLT: when add/average lots of independent things, result tends to follow normal distrubtion

Question 27

68-95-99

Answer 27

• 68% of all observations/measures are between -1 SD and +1 SD
• 95% of all observations/measures are between -2 SD and +2 SD
• 99.7% of all observations/measures are between -3 SD and +3 SD

Question 28

probability

Answer 28

Probability is the proportion of times that an event would occur in an infinitely long series of identical experiments

Question 29

CI

Answer 29

‘95% confident that the mean bp is between 135 and 145 mm Hg’, using ‘confident’ as a technical term.
o Give the formal interpretation: ‘In 95% of repeated experiments, the confidence interval would contain the mean bp.