12c + 12 (3/4c) + 12 (1/2c) shows the total cost for buying 3 phones that each cost c dollars per month for 12 months.

Now, martin can reasonably guess that the standard deviation for the entire population of people at the mall during the time of the survey is $1.50. what is the 95% confidence interval about the sample mean? interpret what this means in the context of the situation where 95 people were surveyed and the sample mean is $8. use the information in this resource to construct the confidence interval.