Which of the following yields a stratified sample?
| a.All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter. |
| b.The best 15 students, according to the opinion of the instructor, in a class are selected. |
| c.All students in a class are grouped according to their gender. A random sample of 8 is selected from the males and a separate random sample of 7 is drawn from the females. |
d,. The first 15 students in a class are selected without replacement.
Which of the following yields a simple random sample?
| a.All students in a class are divided into groups of 15. One student is randomly chosen from the first group, the remaining observations are every 15th student thereafter. |
| b.The best 15 students, according to the opinion of the instructor, in a class are selected. |
| c.The names of 50 students in a class are written on 50 different pieces of paper and put in a hat. The first 15 pieces of paper are selected blindly one at a time without replacing them back in the hat after shuffling the papers thoroughly. |
| d. All students in a class are divided into groups according to the rows in which they are seated. One of the groups is randomly selected |
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