Description of Sample Size

1) In order to set rates, an insurance company is trying to estimate the number of sick days that full time workers at an auto repair shop take each year. A previous study indicated the standard deviation was 2.8 days. How large a sample must be selected if the company wants to be 95% confident that the true mean differs from the sample mean no more than 1 day?

A) 1024 B) 512 C)313 D)141

2) A manufacturer of golf equipment wishes to estimate the number of left handed golfers. How large a sample is needed to be 98% confident that the sample proportion will not differ from the true proportion by more than 5%? A previous study indicates that the proportion of left hand golfers is 8%.

A) 114 B) 41 C) 174 D) 160

3) Fifty five percent of registered voters in a congressional district are registered Democrats. The Republican candidate takes a poll to assess his chances in a two candidate race. He polls 1200 potential voters and finds that 621 plan to vote for the Democratic candidate. Does the Republican candidate have a chance to win? Use a=0.05