general theory questions

Question 1

What tests can be used to compare mean survival time of multiple independent samples?

6

Answer 1

-Berslow-day test
-Mantel Haenszel test
-Weighed log rank test
-Log rank test
-Tarone-ware test
-Green wood test

Question 2

which tests cant be used to compare mean survival time of multiple independent samples?

Answer 2

-Kappa
-Binomial test

Question 3

Properties of density curve

Answer 3

-Bell shaped
-Area under the curve is equal to 1: The total area under the density curve represents the probability of all possible outcomes.
-The curve is positive: The density curve must always be above the x-axis, indicating that probabilities are non-negative.

Question 4

What does the Pearson correlation coefficient measure

Answer 4

Measure the sign & strenght of linear association between 2 continuous variables

Question 5

When to use nonparametric tests based on ranks

Answer 5

When we have ordinal data

Question 6

Which of the following is not a probability?
a) positive predictive
b) value incidence rate
c) relative risk
d) sensitivity
e) lethality

Answer 6

c

Question 7

9.) Which of the following is not a probability?
a) prevalence rate
b) mortality rate
c) positive predictive value
d) odds ratio
e) sensitivity

Answer 7

d

Question 8

12.) What are ranks of the data?
a) Ranks are just the data themselves.
b) Ranks are expected frequencies.
c) Ranks are observed frequencies.
d) Ranks are conditional probabilities.
e) Ranks are natural numbers assigned to sorted sample data.

Answer 8

e

Question 9

13.) Which statement(s) is (are) true?
a) If we reject the null hypothesis we say that the difference is not significant at the given level.
b) The alternative hypothesis is often the one that assumes fairness, honesty, regularity, equality,
lack of effect.
c) If we do not reject the null hypothesis we say that the difference is significant at the given level.
d) The null hypothesis is often the one that assumes fairness, honesty, regularity, equality,
lack of effect.
e) To decide based on a p-value, we compare it to the critical value in the table.

Answer 9

answer : d

e- we compare p-value to significance level if p < significance level then H0 is REJECTED

Question 10

15.) What is the null hypothesis of the one-way analysis of variance (ANOVA)?
a) Several (>2) population means are equal.
b) Several (>2) population variances are unequal.
c) The slope of the line is not 0.
d) Several (>2) sample means are equal.
e) Several (>2) population means are unequal

Answer 10

a

Question 11

16.) Which is true?
a) One property of the density curve that it is always above the horizontal axis.
b) The binomial distribution has two parameters: µ (the mean) and s (the dispersion).
c) One property of the binomial distribution: always bell shaped
d) One property of the density curve that it is always below the horizontal axis.
e) One property of the density curve that it has area exactly 0.5 underneath it.

Answer 11

a

Question 12

from what are the confidence limits?

Answer 12

from the sample data

Question 13

25.) To compare the variance of a continuous variable in two independent groups, what is the
appropriate method?
a) Mann-Whitney U test
b) One-sample t-test
c) Paired t-test
d) Two sample t-test
e) F-test

Answer 13

E

Question 14

if two continuous variables are independents what is their correlation

Answer 14

0

Question 15

what is the assumption of the student’s 2 sample t-test

Answer 15

-independance
-normal distribution
-equal variances

Question 16

if we do not reject is the difference signififcant or not?

Answer 16

not significant

Question 17

assumption of F-test?

Answer 17

-indepedance
-normal distrubtion
-equal variances

Question 18

what is a parameter?

Answer 18

is a number characterizing an aspect of a population (such as the mean of
some variable for the population), or that characterizes a theoretical distribution’s
shape

Question 19

how many and what are the parameters of binominal distribution?

Answer 19

two parameters: n (the number of trials) and p (the
probability of success).

Question 20

43.) Which is true?
a) The Pearson’s correlation coefficient is used to measure the sign and the strength of the linear
association between two continuous variables.
b) The closer the correlation to 1, the stronger the negative linear connection between two
continuous variables.
c) The closer the correlation to 0, the stronger the linear connection between two
continuous variables.
d) The standard deviation is used to measure the sign and the strength of the linear association
between two continuous variables.
e) The closer the correlation to -1, the stronger the positive linear connection between two
continuous variables.

Answer 20

a/ c is wrong because A correlation coefficient of 0 indicates no linear relationship between the two variables. The closer the correlation coefficient is to 1 or -1, the stronger the linear relationship.

Question 21

45.) Which test can be used to compare mean survival time of multiple independent samples?
Mark the correct and false answers.
a) Berslow-Day test (TRUE/FALSE)
b) Kappa (TRUE/FALSE)
c) Mantel-Haenszel test (TRUE/FALSE)

Answer 21

true
false (just like binomial test)
true

Question 22

47.) What is the mean survival time? Mark both the correct and false answers.
a) The probability at time t is that a person randomly selected from the study population is still
alive at that time. (TRUE/FALSE)
b) Mean survival time is estimated by the area under the survival function. (TRUE/FALSE)
c) Mean survival time is estimated by 1-(area under survival function). (TRUE/FALSE)

Answer 22

false
true
false

Question 23

detinition of the cohort (prospective) study

Answer 23

Prospectively examines the effect of a risk factor on the development of an illness, since in the beginning
all individuals were free of the illness. The presence of exposure is known./ assumption of RR

Question 24

49.) Which one of the following statements is correct for the paired-sample t-test?
a) If p < a, then the null hypothesis is to be rejected and the two standard deviations are said to be
significantly different at level of a.
b) If p < a, then the null hypothesis is to be accepted and the two mean values are said to be
significantly different at level of a.
c) If p > a, then the null hypothesis is to be accepted and the two mean values are said to be
significantly different at level of a.
d) If p < a, then the null hypothesis is to be rejected and the two mean values are said to be
significantly different at level of a.
e) If p > a, then the null hypothesis is to be accepted and the two standard deviations are said to be
significantly different at level of a.

Answer 24

d

Question 25

50.) The probability of a Type I error equals what

Answer 25

is equal to the level of significance

Question 26

what is a pandemic?

Answer 26

when an epidemis covers part or the entire earth

Question 27

do we reject or accept if p<significance level

Answer 27

we reject null hypothesis

Question 28

if |t|>t α do we reject or accept

Answer 28

reject

Question 29

if p = 0 we reject or accept H0

Answer 29

reject

Question 30

```

if x² <x²α ; reject or accept H0

Answer 30

accept

Question 31

correct for the independent-sample t-test?

Answer 31

b) If p < α, then the null hypothesis is to be rejected and the two mean values are said to be significantly different at level of α.

Question 32

true about the chi-square test for independence?

Answer 32

c) It assesses the association between two categorical variables.

It does not compare means or variances, and it does not require the assumption of normality.

Question 33

3. In the context of ANOVA (Analysis of Variance), which statement is correct?
   a) If F-statistic is large, the null hypothesis of equal means is rejected.
   b) If p-value is greater than 0.05, the null hypothesis is rejected.
   c) The test is used to compare the variances of two populations.
   d) ANOVA can only be used with two groups.
   e) The test does not require the assumption of normality.

Answer 33

a

Question 34

4. Which statement correctly describes a Type I error?
   a) Rejecting a true null hypothesis.
   b) Accepting a true null hypothesis.
   c) Rejecting a false null hypothesis.
   d) Accepting a false null hypothesis.
   e) None of the above.

Answer 34

a) Rejecting a true null hypothesis.

Explanation: A Type I error occurs when the null hypothesis, which is actually true, is incorrectly rejected. This is also known as a “false positive.”

Question 35

5. In hypothesis testing, the power of a test is:
   a) The probability of rejecting the null hypothesis when it is true.
   b) The probability of accepting the null hypothesis when it is false.
   c) The probability of rejecting the null hypothesis when it is false.
   d) The probability of accepting the null hypothesis when it is true.
   e) None of the above.

Answer 35

c.The probability of rejecting the null hypothesis when it is false.

The power of a test is the probability that it correctly rejects a false null hypothesis. High power means there is a high probability of detecting an effect when there is one (i.e., avoiding a Type II error).

Question 36

6. Which of the following statements is true about the p-value in hypothesis testing?
   a) A p-value of 0.05 means there is a 5% probability that the null hypothesis is true.
   b) A p-value of 0.05 means there is a 5% probability that the observed result is due to chance alone.
   c) A p-value of 0.05 means there is a 95% probability that the alternative hypothesis is true.
   d) A p-value of 0.05 means there is a 95% probability that the observed result is due to chance alone.
   e) None of the above.

Answer 36

b

Question 37

7. Which of the following is an assumption of the one-way ANOVA?
   a) The samples are independent.
   b) The populations have equal variances.
   c) The populations are normally distributed.
   d) All of the above.
   e) None of the above.

Answer 37

ALL

Question 38

10. In regression analysis, the coefficient of determination (R²) represents:
    a) The proportion of the variance in the dependent variable that is predictable from the independent variable(s).
    b) The strength and direction of the linear relationship between two variables.
    c) The correlation coefficient squared.
    d) The slope of the regression line.
    e) Both a and c.

Answer 38

e

Question 39

12. Which of the following best describes a confidence interval?
    a) A range of values that is likely to contain the population parameter.
    b) A range of values that is likely to contain the sample statistic.
    c) A range of values that is certain to contain the population parameter.
    d) A range of values that is certain to contain the sample statistic.
    e) None of the above.

Answer 39

a

Question 40

13. Which of the following is not a requirement for conducting a t-test for the mean?-The population standard deviation must be known.

so what test needs standard deviation

Answer 40

Z-test