Statistical Problem - Essay Example

WRITTEN ASSIGNMENT EXERCISE 1 6 Observational studies can reveal only association, whereas designed experiments can help establish relation 8The study provides inferential statistics. This is because it is stated in the question averages have been calculated in order to compare the average wages for the year 1993 to the average wages for the year 2003 and from the definition of inferential statistics we know that data is termed as inferential if they are being used for comparison purposes or to draw conclusions.1.10The study provides inferential statistics.

This is because a sample is being used to make estimation for an entire population, in other words an inference is being drawn about the population.1.14a. The population is that of adult citizens of the US possessing a motor vehicle powered by gasoline. b. The percentage provided are inferential statistics since the data provided allows to make conclusions concerning the poll conducted.EXERCISE 1.21.30The poll undoubtedly provides inferential statistics which clearly conclude that the vast majority of the people who had taken part in the poll consider staying home and relaxing during the Memorial Day Weekend.

However since it is an online poll, it is difficult to know about the demographical state of those who participated in the poll exactly. Moreover since the poll was conducted during the week end itself it would be rather obvious that all people who were on vacation or at a military cemetery would not be in front of their PC in order to participate in the poll. Hence such a poll would seem very unsuitable, unless if it were carried before the weekend.1.34Simple random sampling is the basic sampling technique where we select a group of subjects (a sample) for study from a larger group (a population).

Each individual is chosen entirely by chance and each member of the population has an equal chance of being included in the sample. Every possible sample of a given size has the same chance of selection.A simple random sample is a subset of individuals (a sample) chosen from a larger set (a population). Each individual is chosen randomly and entirely by chance.EXERCISE 1.31.52aFirstly we know that the table consists of 100 top schools. Hence total can be defined as 100.Secondly we will calculate the percentage of schools for each group(which in this case will be based on the percentages of free lunch) as followsBetween 0 and 10 : 50%Between 10 and 20: 18%Between 20 and 30: 11%Between 30 and 40: 8%Greater than 40: 13%Hence, based on the above, we will know that from our sample of 25 high schools, 50 % shall be in the group Between 0 and 1018 % Between 10 and 2011 % Between 20 and 308 % Between 30 and 4013 % Above 40c.

Based on the above, if we consider the stratified sample of 25 high schools, the number of schools which would be selected with a percent free lunch value between 30 and 40 would be 8% of 25 which equals to 0.08 X 25 = 2.Hence, 2 High Schools would be selected from that stratum.EXERCISE 1.41.60A. The treatment group consisted of patients suffering from depression, OCD and Bulimia Nervosa.B. The control group was the 1331 patients who were given placebo since they were used to compare with effects of Prozac.C. The treatments were the use of Prozac by 2444 patients and placebo for 1331 other patients.