Suppose a church is considering purchasing new hymnals (books that contain the hymns sung during the service) and wants to sample the congregation to see whether its members support the purchase. They might ask those in the sample to choose a number from 1 to 5, where 1 means new hymnals should definitely NOT be purchased, 3 is neutral, and 5 means they should definitely be purchased. Explain why might you want to stratify your samples into two groups: the choir (with other musical performers) and those not in the choir?

So, to avoid biasing, to get an unbiased result we stratify the given sample.

The explanation is done in the explanation section thoroughly.

Step-by-step explanation

When do we stratify?

We stratify the samples when there is no homogeneity in sample. 

Given Sample has 

Here our sample is not homogeneous with respect to response. Since ,the choirs are likely to support the purchase of new hymnals ,

because that's what they like to do , singing, taking part into church services. The main part of choir and other musical performers are to sing hymns, they are most likely to support to buy the new hymnals.

What is the need to stratify our sample?

Stratifying a sample is dividing the sample into sub-groups. Here we divided the groups as choir and those not in the choir.

This is done to avoid biasing, because the people not in the choir may or may not support as it has nothing to do with them, this decision may affect the support given by choir group if they are not separated.

So, to avoid biasing, to get an unbiased result we stratify the given sample.