The ABC battery company claims that their batteries last at least 100 hours, on average. Your ...

The ABC battery company claims that their batteries last at least 100 hours, on average. Your experience with their batteries has been somewhat different, so you decide to conduct a test to see if the company's claim is true. You believe that the mean life is actually less than the 100 hours the company claims. You decide to collect data on the average battery life (in hours) of a random sample of n = 20 batteries. Some of the information related to the hypothesis test is presented below.

Test of H0: mu => 100 versus H1: < 100 

Sample mean 98.5
Std error of mean 0.777

Assuming the life length of batteries is normally distributed, what is the value of the test statistic used to conduct your test of hypothesis?  Place your answer, rounded to 3 decimal places in the blank. For example, -2.345 would be a legitimate entry.