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Flashcards in Multiple Choice Questions Deck (49)
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1

Linear regression...

.. compares the standard deviation of two variables with the equation of the line
.. characterizes the goodness of the parameters of a fitted line
.. gives the parameters of the line best fitting to the data
.. gives the equation and parameters of the best fitting function

gives the parameters of the line best fitting to the data

2

What is our conclusion if we obtain p =3,5 in a two sample t-test?

.. We accept the null hypothesis
.. Nothing, we do the calculation again
.. Since p>1, there is no significant difference
.. We reject the null hypothesis considering 5% level of significance

Nothing, we do the calculation again

3

When should the Kruskall-Wallis-test be used?

.. If we have more than two independent, numerical samples, some or all of which is not normally distributed
.. if we have more than two independent, numerical, normally distributed samples
.. if we have more than two dependent, numerical, normally distributed samples
.. if we have more than two dependent, numerical samples, some of which are nor normally distributed

If we have more than two independent, numerical samples, some or all of which is not normally distributed

4

In a one-sample t-test the calculated t value is 1.897 and the t value that belongs to the significance level is 2.013. What is your conclusion?

- I repeat my calculation, because this situation can not happen in one-sample t-test.
- I accept the nullhypothesis.
- I reject the nullhypothesis.
- I can not say anything without knowing the probabilities.

I accept the nullhypothesis.

5

What is your conclusion when the calculated p-value of an F-test is higher than the significance level?

.. I have to use Mann-Whitney U-test.
.. Variances are equal.
.. Variances are not equal.
.. I can accept the nullhypothesis of two-sample t-test.

Variances are equal.

6

Simply increasing the sample size would not change the number of degrees of freedom …

… in case of the t-test for two independent samples (supposing unequal variances)
… in case of the chi squared test.
… in case of the F test.
… in case of the t-test for two independent samples (supposing equal variances)

in case of the chi squared test.

7

We are executing a two-tailed F-test. Choose the possible outcome.

.. F = 0 and p = 1.
.. F = 100 and p = 1.
.. F = 1 and p = 1.
.. F = –1 and p = 1.

F = 1 and p = 1.

8

I wanted to use a two sample t-test, but it turned out that the measured variable does not follow normal distriubtion. What test can I use?

.. Wilcoxon test
.. Mann–Whitney U-test.
.. one sample t-test
.. F-test

Mann–Whitney U-test.

9

The correlation correlation coefficient is close to one if ...

... the relationship between the variables is linear with positive increment.
... the relationship between the varialbes is function-like.
... the relationship between the variables is linear.
... the relationship between the variables is not significant.

the relationship between the variables is linear with positive increment.

10

The absolute value of the correlation coefficient ...

... is the square of the covariance.
... cannot be zero.
... is the square root of the determination coefficient.
... is the maximum value of the alpha error of the correlation t-test.

is the square root of the determination coefficient

11

Linear regression ...

... characterizes the goodness of the parmeters of a fitted line.
... compares the standard deviation of two variables with the equation of the line.
... gives the parameters of the line best fitting to the data.
... gives the equation and parameters of the best fitting function.

gives the parameters of the line best fitting to the data.

12

What is the reason of the fact that most physiological variables are characterized by normal distribution?

.. They are all related to each other so they must have the same (or at least similar) distribution.
.. In fact, most of them does not follow normal distribution, and we rather deal with those few which do.
.. They are actually transformed so that they would follow normal distribution which makes them easier to be dealt with.
.. They influenced by many independent events, and this, according to the central limit theorem, yields normal distribution.

They influenced by many independent events, and this, according to the central limit theorem, yields normal distribution.

13

In meteorology, the intensity of UV-B radiation is classiefied as follows: weak, moderate, strong, very strong, extreme. What is the type of this data?

.. Not enough information to decide.
.. Exponential.
.. Discrete numerical.
.. Categorial.

Categorial

14

Choose the right statement on type II error.

.. Gives the error of wrong decision.
.. Gives the error of the right decision.
.. The null hypothesis is accepted, although it is false.
.. The alternative hypothesis is accepted, although it is false.

The null hypothesis is accepted, although it is false

15

The probability of event 'A' is 0.71. What is the maximum possible probability of event 'B' if events 'A' and 'B' cannot happen at once?

.. Exactly -0.71.
.. It can be anywhere between 0 and 1.
.. It can be anywhere between 0 and 0.29.
.. Precisely 29%

Precisely 29%

16

Which of the following values cannot be negative?

.. The Z-value in a Mann–Whitney U-test.
.. The correlation coefficient.
.. The t-value in a paired t-test.
.. The F-value in an F-test.

The F-value in an F-test.

17

A test for homogenity is to be conducted. Which method shall be used?

.. Student's t-test for two samples.
.. Chi-square test.
.. Student's t-test for one sample.
.. Mann–Whitney U-test.

Chi-square test.

18

In which case should one reject the null hypothesis?

.. If the absolute value of the statistical parameter calculated from the sample is greater than 5%.
.. If the p-value calculated from the sample is greater than 5%.
.. If the p-value calculated from the sample is greater than the critical p-value.
.. If the absolute value of the statistical parameter calculated form the sample is greater than the absolute value of the critical statistical parameter.

If the absolute value of the statistical parameter calculated form the sample is greater than the absolute value of the critical statistical parameter.

19

What distribution do the data sets follow if we used Wilcoxon test to compare them?

.. Normal distribution.
.. Can be anything different from standard normal distribution.
.. It has a t-distribution with number of dergrees of freedom equal to one minus the sample count.
.. The distribution is either unknown or non-normal.

The distribution is either unknown or non-normal.

20

We are executing a two-tailed F-test. Choose the possible outcome.

F = –1 and p = 1.
F = 1 and p = 1.
F = 0 and p = 1.
F = 100 and p = 1.

F = 1 and p = 1.

NB! T test: t = 0, P = 1

21

We tossed a fair coin 5 times and the outcome was always heads. What is the probability that the outcome of the 6th toss is heads?

.. It is (1/2) ÷ 6 = 1/12.
.. Not enough data to tell.
.. It is (1/2)^6 = 1/64.
.. It is 50%.

It is 50%

22

The consequence of the law of large numbers is ...

... that the standard error of a sample goes to the standard deviation of the corresponding theoretical distribution if the sample size goes to infinity.
... that the median of the sample goes to the mean of the theoretical distibution, if the sample size goes to infinity.
... that the relative frequency of an event goes to its probability if the sample size goes to infinity.
... that the absolute frequency of an event goes to its probability if the sample size goes to infinity.

that the relative frequency of an event goes to its probability if the sample size goes to infinity.

23

What is the most important characteristic of the sample statistical parameters (t, F, z, chi square) from the point of view of hypothesis testing?

.. They can be always calculated from the sample, if the right hypothesis test is used.
.. Their probability density function is known.
.. Their distribution is symmetrical, so both one-tailed and two-tailed probabilities can be calculated.
.. Their value is zero if the null hypothesis is true.

They can be always calculated from the sample, if the right hypothesis test is used.

24

We are studying the applicability of a diagnostic test. What is the name of the parameter given by the ratio of true positive tests and all ill people?

- prevalence
- sensitivity
- segregation
- specificity

Sensitivity

25

Standard normal distribution is identical to ...

... uniform distribution.
... Student's t-distribution with infinity degrees of freedom.
... lognormal distribution.
... the Gaussian distribution.

the Gaussian distribution

26

What is the number of degrees of freedom in case of a correlation t-test, if the sample size is 23?

44
23
22
21

21

27

There is a linear function between y and x, if ...

... y / x is constant
... x = a · y, where a is a constant (the increment).
... the change in y is proportional to the change in x.
... y = a · x, where a is a constant (the increment).

the change in y is proportional to the change in x

28

Which test may be used if the conditions of the chi-square test are not true?

- Kruskall-Wallis test.
- Correlation t-test.
- ANOVA.
- Fisher's exact test.

Fisher's exact test.

29

The probability of occurrence of vascular stenosis among smokers is 0.19. The probability of being a smoker in a given population is 0.29. What is the probability in this population that someone is a smoker with vascular stenosis?

0,655
0,055
Data is too few to answer.
~1

0,055

30

What is your conclusion when the calculated p-value of an F-test is higher than the significance level?

I can accept the nullhypothesis of two-sample t-test.
Variances are equal.
Variances are not equal.
I have to use Mann-Whitney U-test.

Variances are equal.