3.Westfield High School has 2,000 students enrolled . The principal wants to conduct a survey about phone usage during school hours. She decides to ensure representation from each grade level (9th, 10th, 11th, and 12th) and divides her data into these groups before she conducts her survey. What type of sampling is this? a. Random sampling b.Systematic sampling (includes cluster and stratified sampling)

## Step 1<br />The problem describes a situation where the principal of Westfield High School is conducting a survey on phone usage during school hours. She divides the students into groups based on their grade level (9th, 10th, 11th, and 12th). This is a clear example of stratified sampling.<br /><br />## Step 2<br />Stratified sampling is a type of sampling method in which the population is divided into different subgroups or strata, and samples are taken from each stratum. In this case, the strata are the different grade levels.<br /><br />## Step 3<br />The principal is not randomly selecting students from the entire population of 2000 students. Instead, she is dividing the population into strata and then taking samples from each stratum. This is a clear example of stratified sampling.