Please download and use data file: Cholesterol.sav.

A study tested whether cholesterol was reduced after using a certain brand of margarine as part of a low fat, low cholesterol diet. The subjects consumed on average 2.31g of the active ingredient, stanol easter, a day. This data set contains information on 18 people using margarine to reduce cholesterol over three time points.

Variable name	Variable
ID	Participant number
Before	Cholesterol before the diet (mmol/L)
After4weeks	Cholesterol after 4 weeks on the diet (mmol/L)
After8weeks	Cholesterol after 8 weeks on the diet (mmol/L)
Margarine	Margarine type Aor B

Use proper t test to answer the following questions:

1). Are there significant difference in cholesterol after 4 weeks of diet?

2) Did different margarine type yield difference in cholesterol after 8 weeks on the diet?