October 18, 2016

(1) Systematic variation is

Week 12
  1. variation caused by random effects in any direction
  2. variation coming from a factor that introduces bias in one direction only
  3. always deflating the standard deviation
  4. all of the above

(2) The y-axis of a histogram represents…

Week 12
  1. the frequencies
  2. the scores
  3. any metric
  4. none of the above

(3) The standard error…

Week 12
  1. equals the standard deviation divided by the square root of the sample size
  2. estimates the correlation between two variables
  3. equals the mean in most cases
  4. often equals the standard deviation

(4) Pick the variable that is categorical and nominal

Week 12
  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:

Week 12
  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?

Week 12
  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, 11, 15, 19, 20, 22, 24, 30, 31, 39], …

Week 12
  1. the median is 20
  2. the first quartile is 11
  3. the third quartile is 30
  4. the interquartile range is 19
  5. all of the above are correct
  6. only (1) is correct

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

Week 12
  1. About 95%
  2. About 50%
  3. About 4%
  4. less than 4%
  5. Almost zero

(9) You want to find out whether protein content in yogurt (on a continuous scale from 0 to 10) affects the viscosity of the product. What test would you use?

Week 12
  1. A two-tailed Wilcoxon test
  2. A two tailed t-test
  3. A correlation analysis
  4. A regression approach

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

Week 12
  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…

Week 12
  1. whether the residuals are continuous
  2. whether the residuals are homogenous along the fitted values
  3. whether the residuals are normal
  4. all of the above
  5. only (2) and (3) are correct

(12) Which is true for the correlation coefficient?

Week 12
  1. It ranges from -1 to 1
  2. It is not necessarily associated with a p-value
  3. It has nothing to do with the t-statistic
  4. It is the normalised covariance
  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 from such a distribution?

Week 12
  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) In regression analysis, we try to…

Week 12
  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

(15) If in a Chi-squared test with 1 degree of freedom, you obtain a Chi-squared value of 1, this means that

Week 12
  1. your p-value is extremely low
  2. your p-value is clearly not significant (i.e. not below 0.05)
  3. your p-value is above 1
  4. given the information, it is impossible to make a statement on the p-value