PLATO!! Please help! Cara belongs to a knitting group that meets at the local craft shop. From observations, she has hypothesized that people purchase knitting

needles only if they are also purchasing yarn.

To confirm her thinking, Cara surveyed five people who came into the shop at various times throughout the day and asked them about their

past purchases.

Which of these factors is the most likely to skew the results of Cara's observations?

А. The participants are not randomized.

B. The sample size is too small to represent the population,

C. People have to buy yarn at a craft shop.

D. A control group is needed for an observational study.