BEPAS 2.16 Factor vectors + summarizing data

Since our data do not approximate the normal distribution, we will perform a non-parametric test.
In general, the descriptive statistics that are shown together with a non-parametric test are not n, mean and standard deviation, but n, median, percentile 25 and percentile 75.

Adjust the code below to create an R object MVPAbyWalkability: summarize the MVPA_acc by Walkability by calculating the number of cases, the median, percentile 25 and percentile 75 (in that order).