n a study to investigate whether vitamin C will prevent colds, 400 subjects are assigned at random to one of two groups. The experimental group takes a vitamin C tablet daily, while the control group takes a placebo. At the end of the experiment, the researchers calculate the difference between the percentage of subjects in the two groups who were free of colds. This difference is statistically significant (P=0.03) in favor of the vitamin C group.

Step-by-step explanation:

The aim of this question is to see if we can infer and conclude that vitamin C has a good impact in preventing colds based on the evidence provided.

Null hypothesis: Vitamin C has no effect on preventing colds.

Alternative hypothesis: Vitamin C has a strong effect on preventing colds.

Assuming, significance level = 0.05

Since the p-value for the difference is 0.03 which is less than 0.05.

Hence, the null hypothesis is rejected (which is there is no effect of vitamin C).

As a result, it can be concluded that Vitamin C has a major impact on the prevention of colds.

b) the dogs need to shift their focus to human scent.