Match the description/example of each threat to internal validity with the name of the threat that it best represents; The school librarian wanted to study the impact on reading scores of providing reading games on tablets to students. Students from Mrs. Jones's advanced reading group were given tablets with reading games and and those from her remedial reading group were not. Their reading comprehension scores were compared after three months.____ A librarian in a corporation with 400 research scientists calculated the mean number of documents requested from the library by the scientists. He then separated out the 50 scientists with the lowest number of requested documents and calculated that this group of 50 requested a mean of 2.7 documents per month. For the next six months, he sent these 50 "low requesting scientists" a weekly reminder of the services of the library. At the end of this six months, he calculated the mean request for documents by these 50 scientists and found that the average had increased to 3.2 documents. ____ A school librarian carried out a study to see if the number of books read in a semester was related to the number of book talks given by the librarian. During the study, the local public library initiated a read-a-thon with prizes for most books read. ____ Changes within a subject that would occur naturally as a process of time.___ As part of a study to determine whether particular training materials impacted the quality of articles retrieved by 25 clients, four judges used a rating scale from 0-5 to represent the quality of each article. ___ Fifty first grade students were randomly assigned to two treatment groups. During the study, eight of the students in one of the groups came down with measles and missed the entire week of the study.___ A pubic librarian asked the young adults how many e-books they had read in the past two months. They then posted information on the website promoting e-books for two months. They then asked the young adults how many e-books they had read during those two months.___

choose from

instrumental Historical selection Experimental morality Testing Maturation statistical regression