SPSS exercise 4.2

Nowadays, you can buy more or less anything at the supermarket, from drain cleaner to organic oranges. Two Dutch supermarkets, Albert Heijn and Aldi, would like to know whether they should invest in organic/environmentally friendly products. In a survey of 328 people in the Netherlands, one of the things they investigated was interest in products of this type. Do people with a particular preference for one supermarket have a particular interest in these products, or conversely do people with a particular interest in environmentally products have a preference for a particular supermarket?

Generate a contingency table to see if there is an association. First, check the variables to see if all the values are relevant or whether there are any values that should be given as missing. In addition, your analysis should only concern Albert Heijn and Aldi, so ensure you select only these supermarkets (using Select Cases). Put the type of supermarket (prkr) in the columns and the interest in environmentally friendly products (d1ap6) in the rows.

Database: Summo3.sav

a. Interpret the percentage in cell (1.2) (Aldi, very interested).

Of the people who go mostly to Aldi, 33.3% are very interested in environmentally friendly products. If you answer is 30.8%, you forgot to mark 5 (“no input”) as missing

b. What is the most suitable measure of association?

Cramer’s V. There is a symmetrical association because where a person does their shopping could be both the cause and the result of their interest in environmentally friendly products. In addition, one variable is measured nominally ('primary herbs') and the other ordinally ('interest in environmentally friendly products'). The correct measure of association here is Cramer's V.

c. Interpret the value of the measure of association.

The value of the Cramer's V (.13) indicates that there is a weak association between preferred supermarket and interest in environmentally friendly products.

d. Which null hypothesis is being tested here?

In the survey population, there is no association between Dutch people's preferred supermarket and their interest in environmentally friendly products.

e. Have the conditions for a contingency table been met? Explain.

Correct, fewer than 20% (i.e. 12.5%) of the cells have an expected value {= expected frequency} of lower than 5, and there is no value that has an expected frequency of less than 1.

f. Is the association significant? Report the correct data.

No, Chi² (3) = 5.08, p = 0.166.