# Test Yourself

## True or False

### Question 1

The curve illustrating a normal distribution visually expresses the mean and variation of a sample.

### Question 2

The normal distribution is illustrated by a  bell-shaped curve, but it need not be symmetrical.

Label the following distributions:

a)              b)                  c)                  d)

Label the following distributions:

a)                b)              c)

## True or False

### Question 1

The mean can be defined as the sum of the values divided by the number of observations.

### Question 2

The median can be defined as the central value of a group of ordered data.

### Question 3

The interquartile range (IQR) contains the middle 75% of observations

### Question 4

In a normal distribution the mean is equal to the median.

### Question 5

In left skewed data the median is greater than the mean.

### Question 6

The mode is the most frequently occurring value.

The histograms below summarise the hours per week spent on extracurricular activities from a sample of 200 students. Each uses a different bin width.

### Question

Which one do you think best shows the distribution of this variable?

B, C, or D

### Question

What shape is the distribution?

Normal

Positively skewed

Negatively skewed

### Question

What sample statistics might best summarise this distribution in terms of central tendency and spread?

Mean and standard deviation

Median and interquartile range

Mode and range

### Question

How many observations would be expected to lie within the mean plus or minus one standard deviation for a distribution that appeared normally distributed?

Half

Approx 2/3

95%

99%

### Question

In a normally distributed sample of Dutch doctors with a mean height of 1.8m and a standard deviation of 0.1m, which of the following is correct?

Approximately 2/3 of the sample re between 1.6m and 2m tall.

Approximately 97.5% of the sample are shorter than 2.0m.

We’d expect more than 99% of men to be between 1.5m and 2.1m tall.

## True or False

### Question 1

A robust statistic is less influenced by outliers.

### Question 2

The mean and standard deviation are best used when distributions are not symmetrical and contain to outliers because they are less sensitive to outliers (more robust).