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# Sample type, Type II error

1. On Saturdays, cars arrive at David Zebda's Scrub and Shine Car Wash at the rate of 80 cars per hour during the ten-hour shift. David wants a sample of 40 Saturday customers to answer the long version of his quality service questionnaire. He instructs the Saturday crew to select the first 40 customers. His sample is a __________.
a) systematic sample
b) stratified sample
c) simple random sample
d) convenience sample

2. A null hypothesis is p greater than or equal to 0.65. To test this hypothesis, a sample of 400 is taken and alpha is set at 0.05. If the true proportion is p = 0.60, what is the probability of a type II error?
a) 0.45
b) 0.17
c) 0.95
d) 0.67

#### Solution Preview

1. On Saturdays, cars arrive at David Zebda's Scrub and Shine Car Wash at the rate of 80 cars per hour during the ten-hour shift. David wants a sample of 40 Saturday customers to answer the long version of his quality service questionnaire. He instructs the Saturday crew to select the first 40 customers. His sample is a __________.
a) systematic sample
b) stratified sample
c) simple random sample
d) convenience sample