# Question Video: Calculating Information about a Population Based on Stratum Sizes and Proportions Mathematics

In an HR study about the salaries in a certain company with 1,000 employees, the employees were divided into males and females. If the total percentage of females in the company was 60 percent and a sample of 40 people was selected, what was the number of males in the sample?

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### Video Transcript

In an HR study about the salaries in a certain company with 1,000 employees, the employees were divided into males and females. If the total percentage of females in the company was 60 percent and a sample of 40 people was selected, what was the number of males in the sample?

Since the population, that is, the employees in the company, naturally subdivides into two strata, that is, males and females, we use stratified or layered random sampling as our sampling method. This means that any sample should reflect the proportions of the strata within the population. We’re told that 60 percent of the employees were female. A sample of 40 people were selected. And so 60 percent of those 40 must be female.

Since the employees are split into two distinct strata, male and female, if 60 percent are female, then 100 minus 60 percent must be male. That is, 40 percent of the employees must be male. This in turn means that 40 percent of the sample must also be male. And in order to calculate the number of males in our sample, we use the formula 𝑠 is equal to 𝜌 percent times 𝑛, where lowercase 𝑠 is the stratum sample size. 𝜌 is the stratum percentage of population. And 𝑛 is the overall sample size. In our case then, the stratum size for males is 40 percent times 40, which is the sample size, that is, 40 divided by 100 times 40.

Now we can divide both the numerator and the denominator by 10. And once more, dividing numerator and denominator by 10, we have in our numerator four multiplied by four, which is 16. The number of males therefore in the sample is 16.