Question

local salon wants to know if using conditioner before shampoo improves hair texture. They
wash 20 people’s hair daily for a week; half with shampoo first and half with conditioner first. At
the end of the week, participants rate the desirability, smoothness, and silkiness of their hair
using three scales (1 to 10) and add the scores together to assess the treatment effect.
a. Identify the variables of interest.
b. Determine the scale of measurement for each variable.
c. Decide how you are using the variables.
d. Select appropriate test or statistic.

Answer 1

a.

Variables of interest are:

1. Using conditioner first and using shampoo first.

2. Hair texture (Desirability, Smoothness and Silkiness of hair).

b.

Scale of measurement:

For the variables - Using conditioner first and using shampoo first: Nominal scale of measurement.

For the variable - Hair texture (Desirability, Smoothness and Silkiness of hair): Ordinal scale of measurement (from 1 to 10).

c.

Using shampoo first and using conditioner first are used as independent variables.

Hair texture (desirability, smoothness and silkiness of hair) is used as dependent variable.

d.

The Mann-Whitney Test is the appropriate test.