Find Conditional and Marginal Distributions

Find conditional and marginal distributions.
-ASW, a regional shoe chain, has recently launched an online store. Sales via the
Internet have been sluggish compared to their brick and mortar stores, and management
suspects that its regular customers have concerns regarding the security of online
transactions. To determine if this is the case, they plan to survey a random sample of
their regular customers. Under consideration are several plans for selecting the sample.
Name the sampling strategy for each.
a. Regular customers belong to a rewards program and have a customer rewards ID
number. Randomly select 100 numbers.
b. ASW has stores in five different cities in the northeastern U.S. Randomly select one of
the stores and survey all regular customers that belong to its rewards program.
c. ASW has an alphabetized list of regular customers who belong to their rewards
program. After randomly selecting a customer on the list, every 25th customer from that
point on is chosen to be in the sample.
d. Customers are grouped into four age categories (under 21, 21 to 35, 36 to 50, and over
50). Randomly select 10 regular customers in each age category.