Statıstıcs I Ara 3. Deneme Sınavı

As a general rule, most data on monetary values and those coming from physical measurements (e.g., l­ira, gold price, centimeters, and kilograms) are ratio-scale variables.

The ratio of the students whose score under 80 is 0,88

Scatter plot can also be used with a straight line to indicate the correlation between two sets of data. A regression line is added to scatter plot will show a very good indication about the direction of the relationship between two variables. The values of both variables are increasing, hence there is a positive relationship between these two variables. Thus, the straight line tends to have positive slope.

We can obtain some data from an internal data source, such as an organization’s operating and accounting records. These routine data are usually saved in computer data files or databases for efficient entry, storage, and retrieval of information. Internal data is obtained from inside the company for successful operations. The information obtained from internal data source is important to determine the company strategies. We usually obtain data from external data sources. External data sources may be a reference book or statistical periodical published by a government agency, a trade association, or a private service company.

Data come in the form of numbers as well as text, which is something we are discovering more and more. We live in an information world and information is the virtual gold of our society. All observations can be reduced to some numerical quantity, and there are even fields of digital philosophy and digital sociology. (Page 6)

…The key to all of the above is the phrase: “a sample of about 1000 carefully selected people”. 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. (Page 7)

As also understood from the information given, the correct answer is E.

Median cannot be used for nominal data sets.

It is the middle value of an ordered data set and preferred when there are outliers and the distribution is skewed.

The correct answer is D. 

Statistics mainly work on numerical data. Qualitative inquiry is not an interest of statistics.

Dot plot is almost the easiest of the graphs. It can be drawn by hand easily while collecting data. Dot plot will be very useful when the number of objects in our study is rather small such as up to 50 observations. Dot plot is generally used to investigate univariate (quantitative) data, but sometimes it is used to compare two variables. Essentially a dot plot is a one-dimensional scatterplot of observed values of a variable. The correct answer is C. 

The easiest form of data is called categorical, or qualitative, for example data on variables “country” (e.g., the data observation might be Germany) or “question response” (e.g., believe that climate change is manmade) or “exam grade” (e.g., B). Categorical variables and data can be either nominal or ordinal. The question about climate change, with possible responses “natural”, “manmade” or “don’t know/can’t answer” is a nominal categorical variable, as is the variable “country” - there is no ordering in the categories of these variables. By contrast, exam grade is an ordinal categorical variable, since its categories are ordered: A is better than a B, B is better than a C, and so on.

Other examples of nominal categorical variables are gender, region of residence, field of study, type of transport, type of housing, etc.

Other examples of ordinal categorical variables are income group (if incomes have been categorized), an attitude question in a survey where possible responses are strongly agree/agree/disagree/strongly disagree (these categories have an order), social class (with classes usually in an inherent order), terrorist threat levels (in the UK these are low/moderate/substantial/severe/critical), etc.

The other main type of data (see Fig. 1.4) is called continuous, or quantitative, for example data on variables “blood pressure”, “age” and “income”. These are observations of variables on continuous scales, usually rounded in some convenient way. For example, although age is a continuous time variable, and we are getting older all the time by seconds, minutes and hours, someone’s age is almost always rounded to the number of years completed. There is a subtle difference between interval-scale and ratio-scale continuous data, which is worth mentioning here. Age is an interval-scale variable: to compare two children of ages 10 and 12, we would compute the interval difference, i.e. 2 years. We would not say the 12-year old is 20% older than the 10-year old. But comparing prices or incomes, for example, we would tend to compute percentage differences, making them ratio-scale variables. A good example is the inflation rate, comparing the prices of a basket of products over time, not as a difference but as a percentage. As a general rule, most data on monetary values and those coming from physical measurements (e.g., lira, gold price, centimeters, kilograms) are ratio-scale variables.

As also understood from the information given, the correct answer is E.

(60 x 10 % + 50 x 15 % + 70 x 25 % + 80 x 30 % x + 60 x 40 %) / 5 = (6 + 7.5 + 17.5 + 27 + 32) / 5 = 90 / 5 = 18. pg. 85. Correct answer is E.

(64 x 125 x 216)^1/3 = 4 x 5 x 6 = 120. pg. 92. Correct answer is C.

Data come in the form of numbers as well as text, which is something we are discovering more and more. We live in an information world and information is the virtual gold of our society. All observations can be reduced to some numerical quantity, and there are even fields of digital philosophy and digital sociology. It may seem that everything may be recorded and stored somewhere. But in reality - unless we somehow centralize and link all the databases in the world, and have free access to them - we can get access to only a small part of whatever data we are interested in.

'Mean' refers to the average of a set of numbers in the data. The correct answer is C.