The maker of portable phone claims that phone has range of 150 feet with standard deviation of 12. A customer found that the range for her phone was only 130, so she returned the phone saying that either the advertised range was incorrect or there was something wrong with her phone.
An independent research company tests 36 phones and finds out that the average range is 140. Does this show that the company claim is incorrect? Determine the null hypothesis and p-value?