Question

practice questions

1. define stratified sampling in your own words
2. list two merits of stratified sampling.
3. list one demerit of stratified sampling.
4. a school has 500 students: 300 juniors and 200 seniors. a sample of 50 is needed. how many juniors and seniors should be selected?
5. a company has 200 staff: 100 male and 100 female. a sample of 40 is needed. how many from each group?

Explanation:

Step1: Calculate proportion for juniors

The proportion of juniors in the school is \(\frac{300}{500}\).

Step2: Calculate number of juniors in sample

Multiply the proportion by the sample size: \(\frac{300}{500}\times50 = 30\).

Step3: Calculate proportion for seniors

The proportion of seniors in the school is \(\frac{200}{500}\).

Step4: Calculate number of seniors in sample

Multiply the proportion by the sample size: \(\frac{200}{500}\times50 = 20\).

Step1: Calculate proportion for males

The proportion of males in the company is \(\frac{100}{200}\).

Step2: Calculate number of males in sample

Multiply the proportion by the sample size: \(\frac{100}{200}\times40 = 20\).

Step3: Calculate proportion for females

The proportion of females in the company is \(\frac{100}{200}\).

Step4: Calculate number of females in sample

Multiply the proportion by the sample size: \(\frac{100}{200}\times40 = 20\).

Answer:

30 juniors and 20 seniors should be selected.