A study is going to be conducted in which the mean of the lifetime of batteries produced by a certain method will be estimated using a 90% confidence interval. The estimate needs to be within +/- 2 hours of the actual population mean. The population standard deviation is estimated to be around 25. The necessary sample size should be at least _______.

Select answer from the options below

923

100

35

423

21

A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the population mean to within 5 points. The range of population values is 80 and the researcher plans to use a 90% level of confidence. The sample size should be at least _______.

Select answer from the options below

692

216

700

32

44

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS e-mail for non-business communications. A random sample of 200 e-mail messages was selected. Thirty of the messages were not business related. The 90% confidence interval for the population proportion is _________.

Select answer from the options below

0.145 to 0.255

0.255 to 0.265

0.153 to 0.247

0.108 to 0.192

0.091 to 0.209

A large national company is considering negotiating cellular phone rates for its employees. The Human Resource department would like to estimate the proportion of its employee population who own an Apple iPhone. A random sample of size 250 is taken and 40% of the sample own and iPhone. The 90% confidence interval to estimate the population proportion is ____.

Select answer from the options below

0.39 to 0.41

0.35 to 0.45

0.34 to 0.46

0.40 to 0.45

0.38 to 0.42

Life tests performed on a sample of 13 batteries of a new model indicated: (1) an average life of 75 months, and (2) a standard deviation of 5 months. Other battery models, produced by similar processes, have normally distributed life spans. The 98% confidence interval for the population mean life of the new model is _________.

Select answer from the options below

61.60 to 88.41

63.37 to 86.63

79.86 to 81.28

71.77 to 78.23

71.28 to 78.72

The weights of aluminum castings produced by a process are normally distributed. A random sample of 5 castings is selected; the sample mean weight is 2.21 pounds; and the sample standard deviation is 0.12 pound. The 98% confidence interval for the population mean casting weight is _________.

Select answer from the options below

1.76 to 2.66

2.01 to 2.41

2.49 to 2.67

1.93 to 2.49

2.08 to 2.34

Suppose a researcher is interested in understanding the variation in the price of store brand milk. A random sample of 36 grocery stores is selected from a population and the mean price of store brand milk is calculated. The sample mean is $3.13 with a population standard deviation of $0.23. Construct a 92% confidence interval to estimate the population mean.

Select answer from the options below -

$3.06 to $3.20

$3.12 to $3.14

$3.05 to $3.21

$2.90 to $3.36

$3.03 to $3.23