4. A researcher studied the effect of television violence on concentration of a particular blood chemical. In this study, 40 participants were measured over a period of an hour prior to watching a violent show and then immediately after. In the results section, the researcher writes: "There was a significant decline in blood concentration from a mean of 13.41 (SD = 2.48) to 12.38 (SD = 2.69), t(39) = 3.38, p < .01 (one tailed)." Explain this result (including the underlying logic of the computations) to a person who understands hypothesis testing involving a single sample and a known population, but knows nothing about t tests of any kind.
Comment if more explanation is required
The results of this study depicts that if an individual is exposed to media which includes violence over a period of one hour, then they will have reduced levels of the particular blood chemical. This is proven by comparing the means of the data of all the participants before and after watching the violence media and then it was discovered that the difference between the two means is significant which is determined using statistical analysis.
4. A researcher studied the effect of television violence on concentration of a particular blood chemical....
A psychologist wanted to study the effect of television violence on concentration of a particular blood chemical. The psychologist measured the chemical in 40 participants before and after the participants watched a violent show. He reported, "There was a significant decline in blood concentration from a mean of 13.41 (SD = 2.48) to 12.38 (SD = 2.69), t (39) = 3.38, p < .01 (one-tailed)." Mention the statistical test, sample size, critical value, and standard error.