Statıstıcs I Final 7. Deneme Sınavı
Toplam 20 Soru1.Soru
The frequency distribution table of the students’ performance scores of a school were constructed as follows. What is the sample standard deviation of the data?
19,4 |
21,3 |
25,6 |
27,9 |
30,2 |
2.Soru
Data : 4, 4, 5, 5, 5, 15, 15, 18, 19, 15, 4, 5, 14, 14, 17, 17, 26, 26, 22, 22. What is the range of these data ?
4 |
5 |
14 |
26 |
22 |
22 = 26 – 4. pg. 109. Correct answer is E.
3.Soru
Whish is TRUE about the table below specifying types of books a particular customer prefers?
It has the properties of classifying, magnitude, and equal intervals. |
It has a natural or zero-valued base value that cannot be changed. |
It is important that there is no any particular order or ranking for classes. |
The consecutive categories do not represent equal differences of the measured attribute. |
It is considered a nominal scale of measurement. |
Ordinal scales of measurement have the property of both classifying and magnitude. Subjects are categorized into different rank ordered groups. Each value on the ordinal scale has a unique meaning, and it has an ordered relationship to every other value on the scale. From the table, we can conclude that the customer prefers historical fiction to science fiction, science fiction to detective fiction, detective fiction to romance. However, even though the differences in the consecutive numbers of the ranks are equal, we cannot say that how much the customer prefers one type of book over another type. That is, consecutive categories do not represent equal differences of the measured attribute.
4.Soru
In how many different ways can the letters in T H A N K S be arranged?
700 |
720 |
740 |
760 |
780 |
All the six letters in the given word were different, the total number of arrangements would be 6!.
6!=720
5.Soru
What is the variance of the probability distribution given above?
3.62 |
3.20 |
3 |
2.24 |
1.68 |
We have to first compute the mean of the distribution in order to calculate the variance.
Mean=Sum(X.P(X=x))=(1*0.1)+(2*0.2)+(3*0.1)+(4*0.3)+(5*0.2)+(6*0.1)
=0.1+0.4+0.3+1.2+1+0.6=3.6
Variance=Sum(P(X)*(X-Mean)2)=0.1*(1-3.6)2+0.2*(2-3.6)2+0.1*(3-3.6)2+0.3*(4-3.6)2+0.2*(5-3.6)2+0.1*(6-3.6)2=2.24
6.Soru
Suppose that random variable X has exponential distribution with ?=a. Find the probability of P (X ? b) ?
e-a/b |
e-b/a |
-e-b/a |
e-ab |
-e-ab |
f (x) = ? e–?x = a e–ax , x ? 0 ; P( X >= x) = Int(b, sonsuz)(a * e-at dt) = girdi(b, sonsuz)(-e-ax) = 0 - (-e-ab) = e-ab . pg. 213. Correct answer is D.
7.Soru
When the occurrence or non-occurrence of an event A does not affect the occurrence of another event B, then we say that A and B are statistically ........ events?
irrelevant |
codependent |
independent |
dependent |
random |
When the occurrence or non-occurrence of an event A does not affect the occurrence of another event B, then we say that A and B are statistically independent events.
8.Soru
Which of the followings is not true about normal distribution?
Normal distribution is one of the most significant and extensively used continuous probability distribution. |
Normal distribution provides basis for the statistical inference. |
Normal distribution was developed by a mathematician Karl Friedrich Gauss. |
Normal distribution is an asymmetric distribution where the random variable values are uniformly scattered around the mean. |
Normal distribution can be called as “bell curve” or “Gaussian curve”. |
Normal distribution is a symmetric distribution where the random variable values are uniformly scattered around the mean.
9.Soru
Which of the statements below is correct?
I In classical probability, all the outcomes have the same chance of happening.
II In empirical probability, the experiments are repeated many times and the observed outcomes of the event we are interested in is counted.
III When it is not possible to observe the outcomes of events, the researcher applies the researcher assigns a suitable value as the probability of the event.
IV It is not appropriate to use personal judgement to assign the probability.
I and II |
II and III |
II, III and IV |
I, II and III |
II, III and IV |
In the classical probability approach to assign a probability to an event, the assumption is that all the outcomes have the same chance of happening.
The empirical probability uses the relative frequencies to assign the probabilities to the events. The empirical probability is based on experiments. In order to find the probability of a specific event, the experiments are repeated many times and the observed outcomes of the event we are interested in is counted.
Sometimes it may not possible to observe the outcomes of events; therefore, the researcher may assign a probability to an event. In subjective probability approach, the researcher assigns a suitable value as the probability of the event. Therefore, a personal judgement comes in to play to assign the probability. This approach is not favorable method to assign probability, but sometimes if there is no previous knowledge on the subject then the researcher may assign a subjective probability as a starting point. Once enough information about the probability of the event is collected then the researcher may revise this initial subjective probability.
10.Soru
I. For any event A?S, P(A)?0.
II. For any event A, P(A) = 1 – P (A)
III. For any two events A and B, P(A,B) = P(A) + P(B)
Which of the probability axioms can be said to be true?
Only I |
Only II |
I and II |
I and III |
II and III |
The answer is C
11.Soru
Which probability approach uses the relative frequencies to assign the probabilities to the events?
Classical probability |
Objective probability |
Subjective probability |
Positive probability |
Empirical probability |
The empirical probability uses the relative frequencies to assign the probabilities to the events. The empirical probability is based on experiments. In order to find the probability of a specific event, the experiments are repeated many times and the observed outcomes of the event we are interested in is counted. The correct answer is E.
12.Soru
A researcher wants to investigate the effects of tea on heart diseases. What should the researcher do in order to conclude a causal effect?
Ask a sample if they have a heart disease and how much tea they drink a day |
Ask the patients with heart problems whether they are drinking tea |
Give tea to a sample and observe what they are doing |
Conduct an experiment with control and treatment groups |
Survey a sample about their beliefs on the effect of tea on heart diseases |
In order to prove whether tea has an effect on heart diseases, an experiment needs to be conducted where conditions are controlled.
13.Soru
We know that event B has occurred and we are interested in finding the probability of event A. In other words, we are interested in finding the probability of A knowing that event B has occurred. Which of the following formula denotes the probability? We know that event B has occurred and we are interested in finding the probability of event A. In other words, we are interested in finding the probability of A knowing that event B has occurred. Which of the following formula denotes the probability?
P(A∩B) = P(A⏐B)P(B) |
P(A∩B) = P(A⏐B)P(A) |
P(A∩B) = P(A⏐B) |
P(A∩B) P(A)= P(A⏐B) |
P(A∩B) = P(A⏐B)P(B)P(A) |
We know that event B has occurred and we are interested in finding the probability of event A. That is, we are interested in finding the probability of A knowing that event B has occurred.The formula for this is as follows: P(A∩B) = P(A⏐B)P(B)
14.Soru
I. The time a person spends on reading a day
II. The amount of water a person drinks a day
III. The weight gain of a person in a month
Which of the variables given above are examples of a continuous random variable?
Only I |
Only II |
I and II |
II and III |
I,II and III |
Discrete random variables have only a countable number of separate values such as 0, 1, 2 , 3... etc. For example, the number of students in a class for certain day or the number of customers in a supermarket after 5:00 PM are cases for discrete random variables since these variables are finite and countable. Conversely, continuous random variable can take entire infinite values in a given interval. Because of this reason, continuous random variables are commonly measured instead of counted. For instance, waiting time for customers in a supermarket cashier line and travel time of a bus between two points are examples for continuous random variables. The correct answer is E.
15.Soru
The observations are as follows; [14,15,15,16,17,18,20,21,20]
Which of the following is the Pearson’s coefficient of skewness (PCS) value of the data set above?
0,38 |
3,8 |
0,40 |
4 |
0,36 |
PCS = X - mode /s = 3(X - Median)s= 3(17,33-17)/2,54=0.38
16.Soru
I. The air pressure on a tire on an automobile II.The number of students who actually register for classes III. The amount of liquid in a can of cola IV. The temperature of a cup of coffee Which of the variables above are examples of a continuous random variable?
I and II |
I, II and III |
I and III |
I, II ve IV |
I, III and IV |
Discrete random variables have only a countable number of separate values such as 0, 1, 2 , 3... etc. For example, the number of students in a class for certain day or the number of customers in a supermarket after 5:00 PM are cases for discrete random variables since these variables are finite and countable. Conversely, continuous random variable can take entire infinite values in a given interval. Because of this reason, continuous random variables are commonly measured instead of counted. For instance, waiting time for customers in a supermarket cashier line and travel time of a bus between two points are examples for continuous random variables. The correct answer is E.
17.Soru
What is the set for the possible values of the random variable stated below?
"The number of coins that match when three coins are tossed at once."
{1,2} |
{2,3} |
{0,1} |
{0,1,2} |
{1, 2, 3} |
When two coins are tossed at once, some of the possibilities of head or tail can be listed as below:
H(Head) T(Tail)
HHH
TTT
HHT
HTT
When these possibilities are taken into consideration either two or three coins may have the same match. So {2,3}
is the correct answer.
18.Soru
The measures of ________ are another kind of descriptive statistics and give information about the shape of distribution of the observations.
Which option completes the blank in the description above?
Skewness |
Variance |
Standard Deviation |
Interquartile Range |
Box Plot |
The measures of skewness are another kind of descriptive statistics and give information about the shape of distribution of the observations. A data set which is not symmetrically distributed is called skewed. The correct answer is A.
19.Soru
A six-sided fair dice has been thrown 3000 times and the occurrence of number 4 is 450. What is the empirical probability of obtaining a number 4 when you throw a six-sided fair dice?
0,15 |
0,20 |
0,25 |
0,30 |
0,35 |
Empirical Probability of an Event = The number of times the event happens/Total number of observations
P (Number 4)= 450 / 3000 =0,15
20.Soru
Which information below is correct?
I The mean of a continuous random variable X is a weighted
average through the possible values of the random variable and associated probabilities.
II The mean of the continuous random variable is denoted by E (x).
III The mean is also called as expected value and denoted by µ.
IV The variance is denoted by V(x) or ?2.
I, II |
I,III |
I, IV |
II,III |
II, IV |
For the calculation of the mean and the variance for the continuous random variables,only difference is integration substitute’s summation. The mean of the continuous random variable is denoted by µ, the mean is also called as expected value and denoted by E (x). The variance is denoted by V (x) or ?2 and it’s a measure of the scatter or variability for data set. the mean of a continuous random variable X is a weighted average through the possible values of the random variable and associated probabilities. Also, the variance of a continuous random variable X is all squared deviations are weighted with associated probability.
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