Pfeil investigated whether taste acuity declines with age, using a cross-sectional design. Eighty subjects were given a taste acuity test in which they were asked to indicate, for 25 substances, whether the taste was salty, sweet, bitter, or sour. The substances were presented in randomized order. Each person had five scores: four scores corresponding to the correct number of substances identified in the four different taste categories, and one total score for overall correct number. Twenty subjects from each of the following age groups were tested: younger than 40 years; 40 to 55 years; 56 to 70 years; and 71 years and older. Pfeil hypothesized that taste acuity would decline with age, both overall and for all four subcategories of taste. The mean test scores for the four groups on all five outcome measures are presented below, together with information on the statistical tests performed.

AGE GROUP (years)

<40 40-55 56-70 71+ F df p

Salty test 6.3 5.8 5.7 5.4 3.51 3,76 .03

Sweet test 5.0 5.0 5.4 5.2 1.22 3,76 .24

Bitter test 4.0 4.1 3.7 3.3 2.63 3,76 .08

Sour test 1.9 2.0 2.0 2.1 0.89 3,76 .63

Overall test 17.2 16.9 16.8 16.0 2.44 3,76 .10

At what level of measurement was the independent variable operationalized?

d. Could the outcome variables have been operationalized at a higher level?

e. Which age group had the best scores, on average, for the overall test?

f. Which (if any) of the group differences was statistically significant?