Statıstıcs I

Yanıt Açıklaması: In order to create a dot plot one needs to identify the lowest and the highest value of the data set first, then a horizontal axis is drawn and scaled so that it covers the lowest and highest values. A dot plot, essentially, is a simple chart where each observation is presented by a dot along the horizontal axis. If there are repeating observations (multiple occurrences), the dots are stacked up vertically. The dot plots will produce a simple graph of data but at the same time the data itself is never lost, you can easily identify the value of any data point in the dot plot. This is the most powerful aspect of the dot plots. It allows the researcher to show the data in a pictorial form without losing the original information/data. It also gives an opportunity to the researcher to quickly order the data.

Yanıt Açıklaması: password validation. pg. 3. Correct answer is E.

Yanıt Açıklaması: (20 x 3 + 32 x 4 + 47 x 2 + 10 x 3) / 12 = 312 / 12 = 26. pg. 87. Correct answer is B.

Yanıt Açıklaması: Nominal scales of measurement classify things or individuals into qualitatively different classes.  For example, the variable gender has two categories, female and male. Thus, researches could describe sex of the workers using a nominal scale by categorizing people as female and male. Typically, we can use numerals instead of strings to represent individuals’ genders. For example, we can arbitrarily assign number 0 for females and number 1 for males.

Yanıt Açıklaması: The trimmed mean is an arithmetic mean of a data set without extreme values.

Yanıt Açıklaması: Data labeled as successful, average and unsuccessful does not represent a computational score but does represent an order. So, it is an ordinal data.

Yanıt Açıklaması: 9 : median = (12 + 1) / 2 = 6.5 th observation ; then average of 6th and 7th observations : (8 + 10) / 2 = 9

Yanıt Açıklaması: A study that involves Statistics will clearly involve a process of data collection. But there are differences in study objectives which are important to recognize. The main distinguishing factor is whether the study aims to find some evidence of a result or whether it aims to find causes of a result. Medical research is a good context to understand these differences - Statistics in medical research is often called Biostatistics. It is true that many benefits have been detected of taking a low-dosage of aspirin every day. For example, it has been observed that people who take aspirin regularly (less than 300 mg per day) generally have less health problems such as heart attacks, strokes and cancers. The keyword is “observed”: in a community health study involving thousands of people there will be many that take aspirin regularly for problems such as back pain or headaches. For those people it could be observed that they have less chronic diseases compared to people who don’t take aspirin. This is evidence of a difference, but it does not prove that aspirin is the actual cause of the improved health. People who do not take aspirin daily might be poorer and neglect taking medication, and they suffer from more chronic diseases than people with a higher income, so the real difference is socio-economic. From such an observational study it is not possible to conclude a causal effect, it just gives some tentative evidence of a possible relationship between the treatment and the outcome. In order to be able to prove that aspirin is the cause of the improvement in health, an experiment needs to be conducted where conditions are controlled between those taking aspirin and those not taking it. Such an experiment might be designed as follows, restricted to men, for example, since the effects are suspected to be different for men and women. Suppose we take a large group of men in the age group 60- 70 years of age that have no history of chronic disease. We divide them into two groups so that the groups are “balanced” in terms of known factors such as age, social class, and so on (we don’t want one group to have older men than the other). By the way, this “dividing into two groups” is not a trivial matter, but that is a subject for later in this course. Assuming the two groups are comparable, then one group is given the daily low dose of aspirin and the other not, and the groups are followed up for a five-year period and then compared for the incidence of health problems that develop during this time. If the group taking aspirin has less health problems, this would indicate a beneficial effect caused by the aspirin. This type of experiment on people has all sorts of problems, but it is really leading to a conclusion about whether aspirin is the real cause of differences between the two groups. There is the ethical problem of not giving the daily aspirin, which has suspected benefits, to a large group of people. There is also the problem that one group knows it is taking the medication and might change their lifestyle to favour a good outcome by living more healthily. This effect can be eliminated by not telling either group what they are getting and giving the non-aspirin group a so-called placebo, which is medication in the form of an aspirin, so both groups think they are getting the medication. As also understood from the information given, “A study which aims to find some evidence of a result” is an example of observational studies, so the correct answer is A. “A study which aims to find causes of a result”, “A study in which the groups are “balanced” in terms of known factors” and “A study conducted where conditions are controlled” are the examples of experimental studies.

Yanıt Açıklaması: A national sport committe decides to impose stricter conditions for athletes to enter the tournament. One year later, athletes obtain scores that are in general better than those the year before. The increase in scores might be attributable to the introduction of stricter entry conditions.

Yanıt Açıklaması: Anadolu University students is variable, not data

Yanıt Açıklaması: One advantage of the stem-and-leaf display is that it gives the researcher a chance to create a grouped frequency distribution of the data without using any formula.

Yanıt Açıklaması: The outcomes obtained on all variables for one element in the data set is called a case. In this table, the outcomes on the four variables for John constitutes a case.

Yanıt Açıklaması: The way the sample is collected is crucial to obtaining a valid estimate, and this is an important subject which will be dealt with in this course. The main criteria for selecting a sample will be that the sample is representative of the population and that there is no or very little subjectivity in the choice of the sampling units. Sampling is not only conducted by survey researchers on human populations, but also by auditors on a company’s accounts, by agricultural researchers on different pieces of land, and by quality control inspectors on products in a factory, to name only a few examples.

Yanıt Açıklaması: If you want to create a stem-and-leaf display of this data, you need to decide what the stem should be, it is easy to see that all these numbers are the multiples of ten, so the numbers should be 14, 15, 16, and 17. S tems and the leaves should be ordered on each stem from smallest to largest. A vertical line/axis is drawn and on the left hand side of the line/axis stem values are shown as a new row, next we start putting each observation to the right hand side of vertical line according to trailing digits. At last step in each row, the numbers on the right hand side is ordered. Thus the stem-and-leaf plot should be