October 15, 2014

(1) Systematic variation is

  1. variation caused by random effects in any direction
  2. variation coming from a factor that introduces bias in one direction only
  3. always inflating the standard deviation
  4. always deflating the standard deviation
  5. all of the above

(2) The x- and y-axes of a histogram represent…

  1. frequencies
  2. counts
  3. any metrics
  4. none of the above

(3) The standard error…

  1. equals the standard deviation divided by the square root of the sample size
  2. estimates the spread in the sample
  3. equals the mean in most cases
  4. often equals the standard deviation
  5. more than one in the above are correct

(4) Pick the variable that is categorical and nominal

  1. Rank in a 100 m race
  2. Civil status
  3. Numbers of cigarettes smoked per day
  4. Cholesterol level in blood samples (in mg/ml)

(5) Which of the following is not correct:

  1. An independent variable is the same as a predictor variable
  2. A predictor variable can be a factor
  3. A response variable is the same as a factor
  4. A factor can have two or more factor levels
  5. A response variable can be categorical or continuous

(6) Which operation in calculating the variance helps to make sure the latter does not automatically increase with sample size?

  1. Squaring the sum of the differences between observations and the mean
  2. Dividing by the degrees of freedom
  3. Summing up the differences between observations and the mean
  4. All of the above is correct

(7) In this sample: (1, 3, 7, 11, 15, 19, 20, 22, 24, 30, 31, 35, 39), …

  1. the median is 20
  2. the first quartile is 11
  3. the third quartile is 30
  4. the interquartile range is 21
  5. all of the above are correct
  6. only (1) is correct

(8) A population is known to be chi-square distributed with 4 degrees of freedom. What is the chance of finding a value greater than 10?

  1. 95%
  2. 50%
  3. 4%
  4. less than 4%
  5. Almost zero

(9) You want to find out whether protein content in yogurt (low, medium, high) affects the viscosity of the product. What test would you use?

  1. A two-tailed Wilcoxon test
  2. A two tailed t-test
  3. A correlation analysis
  4. An ANOVA approach
  5. A regression approach

(10) In a power t-test, if you increase your sample size AND you decrease your standard deviation,…

  1. you increase your power
  2. you increase your type I error probability
  3. you decrease your type II error probability
  4. you improve your chances to find a difference, should there be one
  5. All but (2) are correct

(11) After regression analysis, we need to check…

  1. whether the residuals are continuous
  2. whether the residuals are homogenous
  3. whether the residuals are normal
  4. all of the above
  5. only (2) and (3) are correct

(12) Which is true for the F-value in ANOVA?

  1. It represents a variance ratio
  2. The higher it is, the lower the associated p-value
  3. It is the between divided by the within-group variance
  4. It depends on the degrees of freedom (sample size within groups, number of groups)
  5. All of the above is correct

(13) Just by sketching a standard normal distribution, what is the probability of sampling a value greater than 2?

  1. the same as sampling a value lower than -2
  2. quite low, maybe a few percent
  3. around 30%
  4. infinitely small
  5. 1 and 2 are correct

(14) A confidence interval tells us…

  1. the probability with which the mean falls in a certain range
  2. the range within which the true mean falls in 95% of cases
  3. the range within which the true mean sits with 95% confidence
  4. none of the above

(15) In regression analysis, we try to…

  1. minimise the sum of squared differences between the observed values and the mean
  2. minimise the distances between the fitted values and the observed values
  3. minimise the sum of squared differences between the fitted values and the observed values
  4. maximise the sum of squared differences between the fitted values and the observed values