Download Theory (10 questions) 1. Displaying the distribution of a

Theory (10 questions)
1.
A
B
C
D
E
Displaying the distribution of a categorical variable
Histogram
Bar chart or pie chart
scatterplot
mean and standard deviation plot
box diagram
2.
What happens to the measures of the dispersion when adding the same number to each data
value?
Adding the same number to each data value in a variable does not change measures of
dispersion
Adding the same number to each data value in a variable shifts each measures of dispersion by
the amount added
Adding the same number to each data value in a variable shifts multiplies measures of
dispersion by the amount added
Adding the same number to each data value in a variable shifts each measures of dispersion by 2
units
Adding the same number to each data value in a variable shifts each measures of dispersion by 2
units to the opposite direction
A
B
C
D
E
3.
A
B
C
D
E
4.
A
Definition of positive predictive value (PPV)
A conditional probability: the probability of a negative test result once the person is healthy
A conditional probability: the probability of a positive test result once the person has the disease
A conditional probability: a probability that someone really does not have the disease once the
test has given a negative result
All of them
A conditional probability: a probability that someone does have the disease once the test has
given a positive result
E
The meaning of a confidence interval
An interval which contains the probability of the (unknown) population parameter is the given
value.
An interval which contains the value of the (known) population parameter with unknown, but
high probability.
An interval which contains the value of the (unknown) population parameter with (given) high
probability
An interval which contains the value of the (known) population parameter with unknown
probability
An interval which contains the sample mean with unknown, but low probability
5.
A
B
C
D
E
What is (are) the assumption(s) of the two-sample t-test?
Independent samples, normality and equality of variances.
Dependent samples, normality and equality of variances.
Independent samples, normality and equality of ranges.
Dependent samples, normality and equality of medians.
Independent samples, equality of medians and variances.
B
C
D
6.
A
B
C
D
E
What is Type II Error?
If a null hypothesis is incorrectly rejected when it is in fact true.
If a null hypothesis is correctly rejected because it is true.
When a null hypothesis is not rejected despite being false.
When a null hypothesis is correctly not rejected because it is false.
When the null- and the alternative hypothesis are also true.
7.
A
B
C
D
E
Which of the following is NOT true for the coefficient of correlation?
If the regression line is decreasing, the coefficient of correlation is negative.
Shows the value of the slope of the regression line
Its value is between -1 and 1 .
If its value is 1, there is a perfect linear relationship between the two variables
If its value is -1, there is a perfect linear relationship between the two variables
8.
A
B
C
D
E
The aim of test of independence.
The three variables are independent or not.
The two variables are independent or not.
Calculate the mean of population.
Make the contingency table.
Calculate the expected frequencies.
9.
A
D
E
Decision of nonparametric tests in case of small sample size (based on tables)
The null hypothesis is accepted when the test statistic (sum of ranks) lies outside the interval
given it table for the test
The null hypothesis is accepted when the test statistic (sum of ranks) lies in the interval given it
table for the test
The null hypothesis is rejected when the test statistic (sum of ranks) lies in the interval given it
table for the test
The null hypothesis is rejected when 0 lies in the interval given it table for the test
The null hypothesis is rejected when 0 lies outside the interval given it table for the test
10.
A
B
C
D
E
Which of following statistic we use to measure agreement?
kappa
alpha
beta
rho
mu
B
C
Correct answers: 1B, 2A, 3E, 4C, 5A, 6C, 7B, 8B, 9B, 10A
Problems and calculations (10 questions)
11.
A
B
C
D
E
12.
A
B
C
D
E
13.
A
B
C
D
E
14.
A
B
C
D
E
15.
A
B
C
D
E
Given the following of the following small sample: X: 4 ; 1 ; 5 ; 4 ;1 , Calculate the mean and
median
Mean=3, median=4
Mean=3, median=5
Mean=5, median=5
Mean=5, median=4
Mean=3, median=3
In a study, a diagnostic test detected 270 true positive and 30 true negative samples of a total
of 300 tests. What is the positive predictive value (PPV) of this test?
PPV is 0.3
PPV is 0.9
PPV is 1
PPV is 1/9
PPV is 0.1
In a study, systolic blood pressure of 10 healthy women was measured. The mean was 119,
the standard error 0.664. Calculate the 95% confidence interval for the population mean!
(α=0.05, ttable=2.26).
Interval is: (124.73, 125.27)
Interval is: (120.89, 123.11)
Interval is: (123.36, 124.64)
Interval is: (117.5, 120.5)
Interval is: (116.84, 121.16)
Systolic blood pressure of 10 healthy women was measured. The sample mean=119, the
standard error=0.664. Supposing that the sample was drawn from a normal distribution, check
whether the population mean is 125! Find the null- and alternative hypotheses.
H0: the population mean is=125, HA: the population mean is not 125
H0: the population mean is not 125, HA: the population mean is = 125
H0: the population mean is=119, HA: the population mean is not 119
H0: the population mean is=119, HA: the population mean is not 125
H0: the population mean is=119, HA: the population mean is 125
First-year medical students were asked about their age. The results: boys: n=78, mean=21.26,
SD=2.98, girls: n=59, mean=19.9, SD=2.454. To test the null hypothesis (H0: the mean age of
boys and girls is the same), what is the appropriate test?
Chi-squared test to test whether the population means are equal.
Independent samples t-test (two sample t-test) to test whether the population means are equal.
One sample t-test to test whether the mean difference between paired observations is zero.
Paired t-test to test whether the mean difference between paired observations is zero.
Paired t-test to test whether the population means are equal.
16.
A
B
C
D
E
17.
A
B
C
D
E
18.
A
B
C
D
E
19.
A
B
C
D
E
20.
A
B
C
D
E
Medical students were asked about their age. Is there a significant difference in the mean age
of boys and girls at 5% level, if the p-value is p=0.0051, the test statistic is t=2.841, the critical
value in the t-table is t0.05,135=1.96?
No, because p = 0.0051 < 0.05.
Yes, because p = 0.0051 < 1.96.
Yes, because p = 0.0051 < 0.05.
No, because p = 0.0051 < 2.841.
Yes, because p = 0.0051 < 0.95.
The correlation coefficient of two variables based on a sample of 10 observations is 0.71. We
want to know if there is a linear connection between the variables. What are the hypotheses
of the test used to answer this question?
H0: ρ = 0, HA: ρ ≠ 0
H0: ρ = 0.71, HA: ρ ≠ 0.71
H0: R = 0, HA: R ≠ 0
H0: ρ = 1, HA: ρ ≠ 1
H0: R = 0.71, HA: R ≠ 0.71
The correlation coefficient of two variables based on a sample of 32 observations is 0.28. We
want to know if there is a linear connection between the variables (at an α level of 0.05).
What is the value of the test statistic?
1.649
1.807
9.114
5.705
1.597
Control and patients with CHD illness were compared. Test the null hypothesis that the illness
is independent of sex. The test statistic is 6.68 (α=0.05, χ2table=3.84).
χ2> χ2table, so the difference is not significant at 5% level, illness is dependent on sex
χ2> χ2table, so the difference is significant at 5% level, illness is independent of sex
χ2< χ2table, so the difference is significant at 5% level, illness is independent of sex
χ2> χ2table, so the difference is not significant at 5% level, illness is independent on sex
χ2> χ2table, so the difference is significant at 5% level, illness is dependent on sex
In a study 40 HPV positive tests of 50 abnormal cervical samples and 10 HPV positive tests of
60 normal cervical samples were detected. Calculate the odds ratio to estimate the risk !
10
15
5
20
2
Correct answers: 11A, 12C, 13D, 14A, 15B, 16C, 17A, 18E, 19E, 20D