Question

7. A wireless company claims that the average of the customers cell phone bill is less than $90.00 per month. A sample of 75 customers reported that their average monthly bill is $84.25 with a standard deviation of $16.03. Test the claim at ∝= 0.005

Answer 1

solution

this is the left tailed test .  

The null and alternative hypothesis is ,

H0 :   = 90.00

Ha : < 90.00

Test statistic = z

= ( - ) / / n

= (84.25 - 90.00) / 16.03/ 75  

= -3.11

P(z < -3.11 ) = 0.0009

P-value = 0.0009

= 0.005  

P-value <

Reject the null hypothesis .

There is sufficient evidence to suggest that