In: Statistics and Probability
A researcher classifies firefighters according to whether their gloves fit well or poorly and by gender. They want to know if there is a difference in the proportion of poorly fitted gloves and gender. At alpha = 0.01, use the chi-square test to determine if there is a difference in the population proportion of glove fitness for the two genders. Using the observed data in the table, determine the percentage of gloves that fit poorly for each gender (fit poorly/total). Which gender has higher percentage of poorly fit gloves? Why?
Observed data |
Males |
Females |
Total |
Gloves fit poorly |
132 |
20 |
152 |
Gloves fit well |
415 |
19 |
434 |
Total |
547 |
39 |
586 |
Expected data |
Males |
Females |
Total |
Gloves fit poorly |
|||
Gloves fit well |
|||
Total |
Expected frequency of a cell = sum of row*sum of column / total sum | |||||||
Expected Frequencies | |||||||
Males | Females | Total | |||||
Gloves fit poorly | 547*152/586=141.884 | 39*152/586=10.116 | 152 | ||||
Gloves fit well | 547*434/586=405.116 | 39*434/586=28.884 | 434 | ||||
Total | 547 | 39 | 586 |
Chi-Square Test Statistic,χ² = Σ(fo-fe)^2/fe =
13.9691
Level of Significance = 0.01
Number of Rows = 2
Number of Columns = 2
Degrees of Freedom=(#row - 1)(#column -1) = (2- 1 ) * ( 2- 1 )
= 1
p-Value = 0.0002 [Excel function:
=CHISQ.DIST.RT(χ²,df) ]
Decision: p-value < α , Reject Ho
conclusion: there is a difference in the population proportion of glove fitness for the two genders
=============
percentage of gloves that fit poorly for male=132/547=24.13%
percentage of gloves that fit poorly for female=20/39=51.28%
Female gender has higher percentage of poorly fit gloves