Dr. DeVries is interested in measuring how practice in problem solving affects this ability. The population of interest is high school seniors, and the sample consists of students who attend an exclusive college preparatory school. Half of the sample receives practice in solving particular types of problems, while the other half does not. Both groups take the same problem-solving test. Which of the following might best explain why Dr. DeVries may not be able to generalize his findings? A) He is not taking into account how the scores on the test might deviate from one another.
B) His data may be positively skewed.
C) He should have conducted his experiment in a lab instead of a natural setting.
D) His sample is not representative of the population.

Indentify 3 problems the early villagers faced

Pollution from a factory that produces cleaning products is an_

Running and sleep. sufficient sleep is important for adolescents for both their neural and psychological development. despite this, daytıme sleepiness and poor physical and psychological functioning related to chronic sleep disturbances are common. there is a growing body of evidence that exercise is associated with both better sleep and improved psychological functioning sixty participants were recruited from a high school in northwesten switzerlandthey were randomly assigned to either a running group or a control group, 30 to each group the running group ran every moming for a little over 30 minutes on weekdays for a three-week period. all participants used a sleep log for subjective evaluation of sleep, and sleep was also objectively assessed at the beginning and end of the study using a sleep electroencephalographic device that measured quantities such as sleep efficiency and time spent in the four different sleep phases. running was found to have a positive impact on both objective and subjective measures of sleep functioning what are the explanatory variable(s) and the response variable(s)? (a) outline the design of the experiment (b) (c) here are some more details on the treatment and control groups. all participants arrived at school at 7 a.m., and the running group did two laps on the track and then ran cross countrv in groups of at least four people for 30 minutes the control group remained seated at the track, worked on horpework. and interacted with each other. when the runners returned, all participants prepared for school and ate a breaktast that was provided. iwhy do you think the experimenters had the control group arrive at 7 am interact withdassmates and have breaktast together? explain. do you think having the control eroup do these activities is important for the types of conclusion that can be reached? how?