Question

A potato chip company claims that their chips have 130 calories per serving. We think this claim is too low, so we buy 40 bags of chips and test the calories per stated serving size. Our sample yields a mean of 132 calories per serving, with a standard deviation of 6 calories. Use alpha = 0.05.

My question is.....Is the manufacturer's claim too low, and why?

Answer 1

x̅ = 132, s = 6, n = 40  
Null and Alternative hypothesis:  
Ho : µ ≤    130
H1 : µ >    130
Test statistic:  
t = (x̅- µ)/(s/√n) = (132 - 130)/(6/√40) =    2.1082
df = n-1 =    39
Critical value :  
Right tailed critical value, t-crit = ABS(T.INV(0.05, 39)) =    1.685
Reject Ho if t > 1.685  
p-value :  
Right tailed p-value = T.DIST.RT(2.1082, 39) =    0.0207
Decision:  
p-value < α, Reject the null hypothesis  
Conclusion:  
There is enough evidence to conclude that manufacturer's claim is too low.