Radka Has Collected Data on the Conditional Mean of Weekly

Radka has collected data on the conditional mean of weekly hours of exercise,comparing those under 75 years of age and those 75 years or older.She observes a higher mean number of weekly exercise hours for the younger group.Because the sample of respondents 75 or older is much smaller than the sample of those under 75,the error bar is much wider for the older than for the younger respondents.Radka needs to check for whether the two groups' error bars overlap,because if they do,

A) that could indicate that the older groups' scores are more highly skewed.
B) it reduces confidence that the observed group differences weren't due to chance.
C) the types of exercise that differ by age could bias reported exercise hours.
D) that could indicate that there is a smaller standard deviation for the older group.