Leo wants to determine the average number of texts middle school students send in a day. Since all middle school students are enrolled in history, he randomly surveyed 4 students from each of Mr. Barnes’s eighth-grade history classes. Ms. Lopez and Mrs. Frank also teach eighth-grade history. What should Leo do to ensure his sample is representative of all middle school students?

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?

Serena is making an experiment. for that, she needs 20 grams of a 52% solution of salt. she has two large bottles of salt water: one with 40% and the other with 70% of salt in them. how much of each must she use to make the solution she needs? i am in need of

Matt had 5 library books. he checked out 1 additional book every week without retuening any books. whats the matching equation