T-distribution

1. The following data are selected randomly from a population of normally distributed values.

40

51

43

48

44

57

54

39

42

48

45

39

43

41

Construct a 95% confidence interval to estimate the population mean.

2.To estimate the average number of customers entering and buying at the supermarket, the supervisor of that supermarket estimated the number of customers visiting every 5 minutes. She randomly selects 5-min intervals and counts the number of arrivals at the supermarket. The figure 58, 32, 41, 56, 80, 45, 29, 32, and 78 were obtained and tallied. The analysis assume that the number of arrivals is normally distributed. Based on these data, compute a 95% confidence interval to have an estimation of the mean value for all 5-min intervals.

Estimating Population Proportions

1. A telecommunications specialist wants to determine the proportion of prepaid subscribers in the Philippines. A random sample of 70 was chosen and data gathered show that 25 are prepaid subscribers. Compute a 90% confidence interval for the proportion of prepaid subscribers in the Philippines.

2.A Study was conducted on the effects of social networking sites among 100 teenagers and found out that 79% of them believed that social networking sites greatly affect their lives. Find a 95% confidence interval for the true proportion for the teenagers whose lives were greatly affected by social networking sites.