Test of two proportions
You may wonder if the amount paid for freight affects whether or not the shipment was late. Recall that in late_shipments dataset, whether or not the shipment was late is stored in the late column. Freight costs are stored in the freight_cost_group column, and the categories are "expensive" and "reasonable".
We can form hypotheses to test.
\(H_{0}\): \(late_{\text{expensive}} - late_{\text{reasonable}} = 0\)
\(H_{A}\): \(late_{\text{expensive}} - late_{\text{reasonable}} > 0\)
p_hats contains the estimates of population proportions (sample proportions) for the "expensive" and "reasonable" groups. ns contains the sample sizes for these groups.
This exercise is part of the course
Hypothesis Testing in R
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
# See the sample variables
print(p_hats)
print(ns)
# Calculate the pooled estimate of the population proportion
p_hat <- ___
# See the result
p_hat