Question 1:

The weight of bags of organic fertilizer is normally distributed with a mean of 60 pounds and a standard deviation of 2.5 pounds. If we take a random sample of 9 bags of organic fertilizer, there is a 70% chance that their mean weight will be less than what value?

Question 2

weights of suitcases checked in at the airport follow a normal distribution with mean 28 pounds and standard deviation 5 pounds. what is the probability that the total weight of a random sample of four suitcases is greater than 120 pounds?

Question 3:

weights of gumballs follow a normal distribution with mean 10 grams and standard deivation 0.8 grams. we take a random sample of 16 gumballs. According to the 68-95-99.7% rule, there is an appromiate 95% chance that the mean weight of the gumballs will be between how many grams?

Question 4:

Suppose that 40% of students at a university drive to campus.

1. If we randomly select 50 students from this university, what is the approximate probability that more than 25 of them drive to campus?
2. if we randomly select 150 students from this university, what is the approximate probability that less than 35% of them drive to campus?

Question 5:

It is calculated that, in order to estimate the true mean amount of money spent by all customers at a grocery store to within $3 with 90% confidence, we require a sample of 50 customers. What sample size would be required to estimate the true mean to within $1 with 90% confidence?

Question 6:

We would like to construct a confidence interval for the mean mu of some population. Which of the following combinations of confidence level and sample size will produce the widest interval ?