In: Statistics and Probability
3. At Phil & Jims steak Shop in Parkside [best cheese steak on the planet] they sell about 750 cheese steak sandwiches per day. | |||||||||
They expect that the mix of sandwiches will be 360 with fried onions only, 165 pizza steask, 120 mushroom steaks & 105 with no cheese. | |||||||||
Last Wednesday they sold 370 with fried onions, 175 pizza steaks, 110 mushroom steaks & 95 with no cheese. | |||||||||
At a 95% level of confidence, did their observations fit with their expectations? | |||||||||
Ho: | fofits fe (observed frequencies are consistent with those expected) | ||||||||
H1: | fo doe not fit fe (observed frequencies are not consistent with those expected) | ||||||||
χ2 = | |||||||||
χ2.05, 3 = | |||||||||
Ho is | accepted/rejected | ||||||||
Conclusion: |
The null and alternative hypothesis is given as:
f0 fits fe , i.e., the observed frequencies(f0) are consistent with those of expected frequencies(fe).
f0 does not fits fe , i.e, the observed frequencies(f0) are not consistent with those of expected frequencies(fe).
Observed and Expected frequencies are given in the question as:
fried onions | pizza steaks | mushroom steaks | No chesse | Total | |
Observed frequency | 360 | 165 | 120 | 105 | 750 |
Expected frequency | 370 | 175 | 110 | 95 | 750 |
The formula for the test-statistic is: with degrees of freedom, df=k-1
The test-statistic is calculated as
Now in the question the confidence level is given as 95% which means the significance level is
The critical value with is:
Since,
Conclusion:
Since the test-statistic is less than the critical value, which means we fail to reject(FTR) null hypothesis H0 . In other words, at , the data does not provide enough evidence to support alternative hypothesis . So we conclude that the observed and expected frequencies for the sandwiches per day are not different.