Explain the difference between a stratified sample and a cluster sample.
a. in a stratified sample, random samples from each strata are included.
b. in a cluster sample, the only samples possible are those including every kth item from the random starting position.
c. in a cluster sample, every sample of size n has an equal chance of being included.
d. in a cluster sample, random samples from each strata are included.
e. in a stratified sample, the only samples possible are those including every kth item from the random starting position.