A simple random sample of 60 items resulted in a sample mean of 80. The population standard deviation is σ = 15. a. Compute the 95% confidence interval for the population mean. b. Assume that the same sample mean was obtained from a sample of 120 times. Provide a 95% confidence interval for the population mean. c. What is the effect of a larger sample size on the interval estimate?

a) (76.21,83.79)

b) (77.32,82.68)    

c) Interval decreases    

Step-by-step explanation:

We are given the following information in the question:

Sample size, n = 60

Sample mean = 80

Sample standard Deviation, s = 15

a) 95% Confidence interval:

Putting the values, we get,

b) Sample size, n = 120

95% Confidence interval:

c) As observed increasing the sample size, the confidence interval become smaller.

the forst and 3rd

step-by-step explanation:

in simplified version   it would be x ≤-4

step-by-step explanation:

multiply each term in x ≤-4 by -1