week 7, population and samples (+ review)

Question 1

What is representativeness?

Answer 1

the degree to which the sample reflects the population

Question 2

What is bias?

Answer 2

Happens when sample characteristics differ from population characteristics (ex of systematic error)

Question 3

How do we ensure that we have done things properly?

Answer 3

1. what is the appropriate sample size?
   2.what is an appropriate sample strategy

Question 4

all members of the population have an …..of being selected

Answer 4

equal chance

Question 5

what is simple random sampling? and what is the process?

Answer 5

everyone has an equal chance of being selected for participation.
1. define the pop
2.list all the members if the population
3.using random process, choose individuals from the list

Question 6

on average, your sample should be representative on every characteristic

Question 7

any difference of the sample should be random, which we can account for with?

Answer 7

statistics

Question 8

what is stratified random sampling and what are the steps?

Answer 8

populations are made of many subgroups (ie sophomore,juniors etc)
1. define population
2.define important strata
3.using random process, select participants from each strata (1/3)

Question 9

what is cluster sampling and what are the steps?

Answer 9

the population of interest has naturally occurring groups, entire groups are being selected
1. define population
2.define naturally occuring groups
3. using random process, select some of the groups

Question 10

what are some violations of random sampling?

Answer 10

lowering the external validity

Question 11

what is external validity? why is it important

Answer 11

it is the likelihood that the result will generalize from the sample to population

Question 12

representative sample ->
non-representative sample->

Answer 12

1. high external validity
2. low external validity

Question 13

What is population distribution

Answer 13

examining the overall spread and characteristics of the dependent variable for the entire group of interest.

Question 14

When does external validity matter the most?

Answer 14

frequency claims,
“45% of american women in their 30’s are very likely to vote for a female president”
- probability sampling ins a must

Question 15

When does external validity not matter?

Answer 15

asssociation/causal claims,
“american women in their 30’s are more likely to vote for a female president when they have more yrs of education”
-nonprobability sampling is okay
-random assignment is key

Question 16

the validity of frequency claims and association/causal claims depend on different factors

Question 17

what are examples of non-probability sampling?

Answer 17

1. haphazard/convenience sampling: using the first people we come find to complete the sample
   2.quota sampling: using the first people we encounter BUT in a specific proportion (ie first 15 men and women)

Question 18

are these violations always a problem? when are they and when are they not?

Answer 18

ex for political pollsters, they care about getting accurate numbers for whole population (frequency claims)

experimental psychologists dont care because they care about understanding how things are connected, not exact numbers (association and causal claims)

Question 19

what does sample size influence

Answer 19

accuracy and reliability of our estimates

Question 20

50:50 is a true proportion

Question 21

what is difference between random sampling vs random assignment

Answer 21

random sampling -> how will you choose ppl to be in your study,, a study that uses random sampling may or not be experimental or not

random assignment -> how you divide the ppl already in your study into dif groups, not a true experiment unless random assignment is used