samples and proportions

Question 1

uses of standard error

Answer 1

estimate how theoretical sample proportions cluster around population proportion

Question 2

what is the distribution of theoretical sample proportions affected by

Answer 2

sample size

Question 3

the larger the sample the … the sample proportions cluster around the population proportion

Answer 3

closer

Question 4

standard error of a mean

Answer 4

use the pop sd and sample size to calculate

Question 5

standard error of a proportion

Answer 5

use pop proportion and sample size to calculate standard error

Question 6

standard error equation for proportions

Answer 6

square root of pop proportion(1-pop proportion) / n

Question 7

example of standard error for pop proportion

Answer 7

proportion = 0.39
sample size = 51
square root of
0.39(1-0.39) / 51
= 0.07

Question 8

calculate z value using pop proportions

Answer 8

sample proportion = 0.63
pop proportion = 0.39
SE = 0.07
z = (0.63-0.39)/0.07
= 0.24/0.07
=3.43

Question 9

z value calculation using proportions

Answer 9

observed sample prop - population prop) / SE

Question 10

point estimate

Answer 10

estimation of population mean

Question 11

what is a good estimate of population mean

Answer 11

sample mean

Question 12

how can you be sure sample mean is a good estimate for pop mean

Answer 12

calculate and interval estimate (confidence interval) to give us greater confidence

Question 13

confidence interval

Answer 13

an interval where we can say a certain level of confidence the value we are estimating lies between 2 values

Question 14

conventional confidence interval levels

Answer 14

95% or 99%

Question 15

confidence interval equation

Answer 15

95% or 99% (sample mean) +- z value x (sd / square root n)

Question 16

confidence intervals with proportions (95%)

Answer 16

p+=( 1.96 * square root of (p(1-p) / n ))

99% uses 2.58

Question 17

when can you use the sample SD as an estimate of population SD

Answer 17

if data normally distributed
sample size greater than 30