Hypothesis Testing
The Operations Manager of a small manufacturing company believes that the number of defective flash drives per week is less than seven. Using the data provided from the last 30 weeks we can test the hypothesis to determine whether or not the claim by the Operations Manager is valid.
Using descriptive statistics in Microsoft Excel, I found the mean to be 7.0333 and the standard deviation to be 1.376736. Then, using the Graphpad calculator I inputted both of these values to run the t-test. Using seven as the “hypothetical mean”, we found the results to be as follows.
P value and statistical significance:
The two-tailed P value equals 0.8954
By conventional criteria, this difference is considered to be not statistically significant.
Confidence interval:
The hypothetical mean is 7.00000000
The actual mean is 7.03333000
The difference between these two values is 0.03333000
The 95% confidence interval of this difference:
From -0.48075187 to 0.54741187
Intermediate values used in calculations:
t = 0.1326
df = 29
standard error of difference = 0.251
In conclusion, it would not be accurate for the Operations Manager to make a claim that the number of defects per week is less than 7. The mean clearly shows that it just above 7.