A business consultant wanted to investigate whether providing daycare facilities on the company premises would reduce the absentee rate of working mothers with children aged 6 years or younger. She took a random sample of 35 mothers who work at companies that provide daycare facilities on the premises, and found that mothers missed an average of 4.2 days from work last year with a standard deviation of 3.78 days. She took random sample of 40 mothers working at companies that do not provide daycare facilities, and found that these mothers missed an average of 7.8 days last year with a standard deviation of 10.65 days. Construct a 98% confidence interval for the difference in the true mean number of days missed for the two populations (rounded off to two decimals).
A business consultant wanted to investigate whether providing daycare facilities on the company premises would reduce the absentee rate of working mothers with children aged 6 years or younger. She took a random sample of 35 mothers who work at companies that provide daycare facilities on the premises, and found that mothers missed an average of 4.2 days from work last year with a standard deviation of 3.78 days. She took random sample of 40 mothers working at companies that do not provide daycare facilities, and found that these mothers missed an average of 7.8 days last year with a standard deviation of 10.65 days. Construct a 98% confidence interval for the difference in the true mean number of days missed for the two populations (rounded off to two decimals).
- A. [-7.79 ; 0.59]
- B. [-7.80 ; 0.68]
- C. [-6.56 ; -0.63]
- D. [-7.30 ; 0.10]
Two groups of males are polled concerning their interest in a new electric razor that has four cutting edges. A sample of 64 males under the age of 40 indicated that only 12 were interested, while in a sample of 36 males over the age of 40, only 8 indicated an interest. Construct a 95% confidence interval for the difference between age-group proportions. The limits of the confidence interval (rounded off to two decimals) are:
- A. [-0.34 : -0.06]
- B. [-0.20 : 0.13]
- C. [-0.11 : 0.01]
- D. [-0.42 : 0.02]
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