A statistics instructor wants to measure the effectiveness of his teaching skill

Question

A statistics instructor wants to measure the effectiveness of his teaching skills in a class of 81 students

(N = 81).

He selects students by waiting at the door to the classroom prior to his lecture and pulling aside every third student to give him or her a questionnaire.

(a) Assuming that all students attend his class that day, how many students will he select to complete the questionnaire?
students

(b) Is this sample design an example of random sampling? Explain.

Yes, because each student has an equal chance of being selected, and each student is replaced before selecting another student.No, because each student is not selected at random, and each student is not replaced before selecting another student.

Explanation / Answer

A:) We can simply find the answer by dividing 81/3 as every 3rd student is being selected so firstly he selects 3rd guy after that he select 6th guy similarly so answer is 81/3 is 27.

B:) No, It's not Random Sampling Because you are selecting each Sample at a fixed interval so there is a lack of Randomness in the sample.this is an example of systematic sampling as in this sampling first unit is selected at random then other units are selected automatically predetermined pattern. It is more convenient than the simple random sampling.

thanks :)

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