Lecture 1

Question 1

What do accuracy and precision mean?

Answer 1

Accuracy is how close the sample mean is to the population mean

Precision is how close individual samples are to the sample mean

Question 2

What are the two conditions for random sampling?

Answer 2

1. Every unit in the population must have an equal probability of being included in the sample
2. Selection of units must be independent (meaning: the selection of a unit must have no effect on the probability of any of the other units being selected)

Question 3

What are the types of variables?

Answer 3

1. Categorical
   - Nominal: not ordered (eg fruit species, sex)
   - Ordinal: ordered (eg military rank, life stage)
2. Numerical
   - Continuous: weight, size, blood pressure (can take on any value in a certain range)
   - Discrete: number of offspring, amino acids in a protein (a whole number)

Question 4

What does a histogram describe?

Answer 4

A histogram describes the frequency distribution of the data.

Question 5

When are relative frequencies useful to use?

Answer 5

Relative frequencies are useful when sample sizes are very different.

Question 6

What is a binary variable?

Answer 6

A binary variable is a variable that can only take on two values: 0 and 1 (eg alive and dead)
Average is the proportion of cases with value of 1

Question 7

What is the difference between the mean and the median?

Answer 7

Median: middle value of the data
Mean: The value you calculate for the sample (add everything up/n)

Question 8

When is the median a better measure of the central tendency than the mean?

Answer 8

When the data is highly skewed.