Question

According to a 2009 Reader's Digest article, people throw away about 9% of what they buy at the grocery store. Assume this is the true proportion and you plan to randomly survey 122 grocery shoppers to investigate their behavior. What is the probability that the sample proportion does not exceed 0.10?

Standard Deviation of Sample Proportion:     

Answer format: .####

z score:      Answer format: .####

Probability:     Answer format: .####

Note: You should keep standard deviation of phat #, z score and probability to 4 decimal places in your calculations.

Use TI 84 to get the probability.

Answer 1

Solution:

Given:

p = 0.09

n = 122

We have to find: the probability that the sample proportion does not exceed 0.10

That is:

Standard Deviation of Sample Proportion:   

z score:

Probability:

Use following TI 84 steps to find probability:

Press 2ND and VARS

Select normalcdf(

Enter Numbers:

.

Since we have to find:

lower limit is minus infinity , thus we enter lower as -9999999, and for - sign , press (-) button.

Enter Upper as obtained z value 0.3861

Mean is 0 and standard deviation is 1 for z.

Click on Paste and press Enter two times

thus we get: