Sampling distributions

Question 1

describe the three steps involved in obtaining and graphing a sampling distribution

Answer 1

1. obtain several samples of the same size
2. for each sample, calculate the mean of a particular variable.
3. graph the means on a histogram –> sampling distribution

Question 2

standard error is a property that specifically describes

Answer 2

sampling distributions

Question 3

standard error formula?

Answer 3

SE = SD (pop or sample) / square root n

Question 4

which SD is the default?

Answer 4

population

Question 5

when sample size is large, what happens the sampling distribution in terms of:

shape of curve
sample mean
standard error

Answer 5

becomes more normally distributed (less skewed)
sample mean nears pop mean
standard error nears pop SD

Question 6

describe central limit theory

Answer 6

with a large pop

• sampling dist becomes more skewed
• sample mean nears pop mean
• sample SE nears pop SD

Question 7

how do you know they’re asking a statistical question relating to sampling distributions?

Answer 7

it will mention:

• a RANDOMLY SELECTED SAMPLE
• pop mean
• usually pop SD, sometimes sample SD
• prob of being above X

Question 8

what happens if they give you POP sd

Answer 8

first calculate SE: = pop SD / sr n
then calculate Z score (X - pop mean / SE)
then calculate probability using Z score table

Question 9

what happens if they give you SAMPLE sd

Answer 9

first calculate SE: sample SD / sr n
then calculate T score: X - pop mean / SE
then calculate DF
then calculate probability using T score table (one tailed)

Question 10

if degrees of freedom are

• above 120
• between values

Answer 10

use infinity

use the closest value