Toothbrushes are an important tool to prevent periodontal (gum) disease and consumers have different types to choose from. A 2018 study recruited 57 healthy young adults and randomly assigned them to 3 types of toothbrush. For an entire week, participants were asked to brush their teeth twice a day with the toothbrush provided. Based on comprehensive oral exams, the change in gum health was assessed for each participant (a positive value represents an improvement).
Toothbrush type Mean (stdev)
Multi-angle bristles 0.030 (0.040)
Circular bristles 0.033 (0.049)
Z-shaped bristles 0.012 (0.028)
State the null and alternative hypothesis.
The P-value for the relevant test is 0.2311. For the healthy young adult population, the study …
A) found strong evidence that mean gum health change is different for each brush type.
B) found strong evidence that mean gum health change isn’t the same with all 3 brush types.
C) failed to find evidence that mean gum health change is the same regardless of brush type.
D) failed to find evidence that mean gum health change differs depending on brush type.
E) We cannot conclude using this P-value because the conditions for inference are not met.
