10 Sampling Methods and External Validity

Question 1

external validity related to:

Answer 1

induction (generalize findings to other pop./setting

Question 2

what is sampled in study>

Answer 2

info to collect, procedures to collect info, research location, clinicians/researchers involved, subjects

Question 3

sample =

Answer 3

subset

Question 4

sample needs to be ___

Answer 4

representative

Question 5

sci and clin research generally use these types of sampling:

Answer 5

incidental, random

Question 6

what is incidental sampling?

Answer 6

selection of most readily accessible members of target pop.; cheapest and easiest

Question 7

what is quota sampling?

Answer 7

know in advance have important subgroups in population; need know which pop. groups important to question, proprtion of diff groups in pop.

Question 8

what is random sampling?

Answer 8

construct list of all members of pop., use method to select randomly from list, all members of pop. have equal chance of selection

Question 9

in random sampling, if need to select ___ may introduce __

Answer 9

replacements; bias

Question 10

advantages of random?

Answer 10

since know sample and pop. sizes, can estimate how representative is sample

Question 11

disadvantages of random?

Answer 11

need to list all population, costly

Question 12

what is stratified random sampling?

Answer 12

like quota, but with random sampling for each subgroup

Question 13

advantages of strat. random?

Answer 13

important groups proportionately represented (very important when key subgroups in low proportion), know exact representativeness whch is important for stats

Question 14

disadvantages of strat. random?

Answer 14

need to list all of population, characteristics, and proportion; cost; gain in accuracy small relative to simple random

Question 15

what is area sampling?

Answer 15

sample on basis of location with known characteristics, randomly select in location and don’t need list of members

Question 16

area sampling is effective cheap method for ____

Answer 16

social surveys (in person or over phone)

Question 17

what is systematic sampling?

Answer 17

choose every 10th case from a list of pop. (not true random)

Question 18

what does systematic assume?

Answer 18

list not made systematically coinciding with sampling system

Question 19

systematic sampling ex. in clinic:

Answer 19

taking temperature and blood pressure every hour

Question 20

what is an optimal sample size?

Answer 20

adequate to make correct infnerences to pop.

Question 21

the discrepancy tween true pop. parameters and sample statistic

Answer 21

sampling error

Question 22

what are two types of external validity?

Answer 22

population and ecological

Question 23

what is population validity?

Answer 23

generalization to sample’s population

Question 24

pop. validity depend on:

Answer 24

how representative is sample, may not always have access to whole target pop.

Question 25

what is ecological validity?

Answer 25

extent results can be generalized to other situation

Question 26

ex. of eco validity?

Answer 26

in vivo vs. in vitro, different institutions