# Sampling Distribution of Sample Proportion

1) A store has determined that 25% of all sales are credit sales. A random sample of 75 sales is selected. What is the probability that the sample proportion will be:

a) greater than .34?

b) between .196 and .354?

c) less than .25?

d) less than .10?

2) 10% of items produced by a machine are defective. A random sample of 100 items is selected and checked for defects. What is the probability that the sample will contain:

a) more than .025?

b) less than .13 defective units?

https://brainmass.com/statistics/probability/sampling-distribution-sample-proportion-406061

#### Solution Preview

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Probability questions/need answers, but explanation of solution

1) A store has determined that 25% of all sales are credit sales. A random sample of 75 sales is selected. What is the probability that the sample proportion will be:

Answers

Let X be the proportion of credit sales. Then X can be assumed to be normal with mean, µ = ...

#### Solution Summary

The solution provides step by step method for the calculation of probability using z score. Formula for the calculation and shaded graph are also given. Machine defection rates are examined.