chapter 10

Question 1

the 2 samples of n1 form pop 1 and n2 from pop 2- the 2 samples taken separately and independently are called

Answer 1

independent simple random samples

Question 2

What is the point estimator of the difference b/w 2 pop means

Answer 2

xbar 1 - xbar 2

Question 3

what is the random sample size adequate for most applciaitons of interval estimation and Hype test procedures

Answer 3

n1 greater than or = 30

n2 greater than or = 30

Question 4

when one or both sample sizes are less than 30 for the difference b/w 2 pop means

Answer 4

the distribution of the pop becomes important

Question 5

when using the t-distribuiton for typ test Q1 and Q2 unknown

Answer 5

remember to always round the df down before using the t-distribution

Question 6

whenever possible what sizes of n1 and n2 are recommended when Q1 and Q2 are not known

Answer 6

equal sizes of n1 and n2 are recommended

• the total samples size is at least 20 (n1 + n2)
• can be expected to provide very good results even if the pops are not normally distributed

Question 7

what is the other approach when Q1 and Q2 are not known

Answer 7

• the two sample sd are combined to provide the pooled sample variance

Question 8

how do you calculate the degrees of freedom for a pooled variance

Answer 8

n1 + n2 -2

Question 9

what is the problem with the pooled sample variance

Answer 9

it is often difficult to verify that both sd are equal

- the pooled sample variance may not provide satisfactory results especially if the sample size are quite different

Question 10

what is the problem with the pooled sample variance

Answer 10

it is often difficult to verify that both sd are equal

- the pooled sample variance may not provide satisfactory results especially if the sample size are quite different

Question 11

describe the independent sample design

Answer 11

a simple random sample of workers is selected and each worker in the sample uses method 1
- a second independent simple random sample of workers is selected using method 2

• test of the diff b/w 2 pop means is based on procedures used in prevoiusly

Question 12

describe the matched sample design

Answer 12

• one SRS of workers is selected
• each worker 1st uses one method and then uses the other method
• the order of the 2 methods performed is assigned randomly
• each worker provides a pair of data values
• each method is tested under similar conditions
• this often leads to a smaller sampling error than independent sample design b/c same workers are sued for both methods

Question 13

which method (independent or matched design) leads to smaller sampling error

Answer 13

matched sample

Question 14

what is the key to the matched sample design method

Answer 14

we only consider the column of differences

Question 15

what is the formula for test stat for hyp test involving matched samples

Answer 15

t = dhat - Md / Sd/ square root n

Question 16

how do you calculate the degrees of freedom for matched samples

Answer 16

n-1

Question 17

when finding the t-value for matched samples design, what is the area

Answer 17

it will likely be between 2 numbers

if it is a 2 tailed test, you double these numbers

Question 18

if the sample sizes are large enough that n1p1, n1(1-p1) and n2p2 and n2(1-p2) are all greater than or = to 5
the sampling distribution of phat 1 - phat 2 can

Answer 18

be approximated by a normal distribution

Question 19

For the difference in pop, when P is NOT KNOWN, what do we do

Answer 19

we pool, or combine the point estimates from the 2 samples (p1 and p2) to get a single point estimator of p as

phat = n1phat1 + n2phat2 / n1 + n2

Question 20

What is this formula phat = n1phat1 + n2phat2 / n1 + n2

Answer 20

weighted avg of phat 1 and phat 2

also called the pooled estimator of p

Question 21

wiehn using a pooled estimate of p, and finding the area, what do you do when it is a two tailed test

Answer 21

you multiply the area by 2

Question 22

If we are interested in testing whether the proportion of items in pop 1 is larger than the proportion of itmes in pop 2, the altnerative hyp should state

Answer 22

P1 -P2 <0