Introduction to Statistical Reasoning
Study 1: A researcher was interested in whether intelligence level depends on body weight. 1000 people were selected from a group of volunteers and divided in 4 groups. The first 250 were considered under-weight, second group of 250 were below average weight, another 250 over the average and the last group of 250 over-weight. The subjects underwent a comprehensive cognitive and psychological examination and scores (integer the range 0 to 200) were assigned to all subjects.
Study 2: A technician is interested in the effects of using different baking temperatures on the impact strength of particle board. 20 boards are randomly allocated to 20 different baking temperatures. After the boards are baked, they are sent to a laboratory where the impact strengths are measured.
Study 3: The manager of an auto repair shop is interested in whether using a new diagnostic machine will speed up the regular servicing of cars. There are two mechanics working on regular services, one with 8 years experience while the other mechanic had only 2 years experience. One mechanic was told to use the diagnostic machine on the next 10 cars she serviced, but not use it on the following 10 cars. The other mechanic was told not to use the diagnostic machine on the next 10 cars he serviced, but to use it on the following 10 cars. Each mechanic recorded the time it took to complete the services for each of these jobs.
Study 4: A sociologist is interested in comparing the exam results
for male and female students on 10 different subjects. The proper authority
was contacted to obtain the numbers of male and female students who took
the exam and the numbers of male and female students who got each of the
grades A, B, C and D.
42, 47, 46, 35, 43, 39, 38, 40, 50, 37, 68, 37, 47, 44, 49
41, 34, 38, 41, 36, 42, 38, 38, 58, 34, 32, 42, 49, 52.