In: Statistics and Probability
Skin care products are big business. A marketing department wants to know whether the age of a person is related to the importance people place on appearance. They administer an online survey and asked participants How important is “Seeking the utmost attractive appearance” to you using a 7-point scale. Do older people feel as strongly as younger people that personal appearance is important?
13-19 | 20-29 | 30-39 | 40-49 | 50-59 | 60+ | Total | |
7 - Extremely Important | 396 | 337 | 300 | 252 | 142 | 93 | 1520 |
6 | 325 | 326 | 307 | 254 | 123 | 86 | 1421 |
5 | 318 | 312 | 317 | 270 | 150 | 106 | 1473 |
4- average importance | 397 | 376 | 403 | 423 | 224 | 210 | 2033 |
3 | 83 | 83 | 88 | 93 | 54 | 45 | 446 |
2 | 37 | 43 | 53 | 58 | 37 | 45 | 273 |
1 - not at all important | 40 | 37 | 53 | 56 | 36 | 52 | 274 |
Total | 1596 | 1514 | 1521 | 1406 | 766 | 637 | 7440 |
If the calculated test statistic is 170.7762, what would the interpretation be using alpha .05?
Solution:-
State the hypotheses. The first step is to state the null hypothesis and an alternative hypothesis.
H0: The age of a person and importance people place
on appearance are independent.
Ha: The age of a person and importance people place on
appearance are not independent.
Formulate an analysis plan. For this analysis, the significance level is 0.05. Using sample data, we will conduct a chi-square test for independence.
Analyze sample data. Applying the chi-square test for independence to sample data, we compute the degrees of freedom, the expected frequency counts, and the chi-square test statistic. Based on the chi-square statistic and the degrees of freedom, we determine the P-value.
DF = (r - 1) * (c - 1) = (7 - 1) * (6 - 1)
D.F = 35
Er,c = (nr * nc) / n
Χ2 = 170.7762
where DF is the degrees of freedom.
The P-value is the probability that a chi-square statistic having 2 degrees of freedom is more extreme than 16.2.
We use the Chi-Square Distribution Calculator to find P(Χ2 > 170.76) = less than 0.0001
Interpret results. Since the P-value (almost 0) is less than the significance level (0.05), we have to reject the null hypothesis. Thus, we conclude that there is a relationship between the age of a person and importance people place on appearance