Dr. Sun is studying the effects of full-contact college sports on athletes’ IQ. She starts with 50 freshman football and rugby players at the start of their first fall semester, and plans to re-test them every fall semester for the next 4 years. What source of error could affect the results of this study?

Sampling error

Explanation:

Dr. Sun is bound to have sampling error affect the result of his study. This is because sampling error in research is said to occur when a researcher just takes a random sample, usually a small number of the population of the study and chooses to study this sample rather than observing every subject that makes up the population. Researchers tend to use small number of a population when the population is large and this becomes the best option, thus making it difficult to avoid sampling error.

giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.