Stat Exam 1

The Empirical Rule states that the approximate percentage of measurements in a data set (providing that the data set has a bell shaped distribution) that fall within two standard deviations of their mean is approximately:

95%.

In a negatively skewed distribution, which of the following is the correct statement?

The distance from the smallest observation to is larger than the distance from to the largest observation

Which of the following statements is true for the following observations: 7, 5, 6, 4, 7, 8, and 12?

The mean, median and mode are all equal.

Which measure of central location and variability are considered to be resistant t extreme values?

The median and interquartile range

Which measure of central location is meaningful when the data are ordinal?

The median.

Generally speaking if two variables are unrelated (as one increases, the other shows no pattern), the covariance will be:

a postitive or negative number

Which of the following statistics is a measure of central location?

A. The mean. B. The median. C. The mode.

Which of the following is correct about the shape of distribution?

A. The shape can show you how many modes there are. B. The shape can help you determine the approximate center of the distribution. C. The shape can help you determine whether the data are close or spread out.

Which of the following statements is true?

A. When the distribution is positively skewed, mean > median > mode. B. When the distribution is negatively skewed, mean < median < mode. C. When the distribution is symmetric and unimodal, mean = median = mode.

Which of the following statements about the mean is not always correct?

Half of the observations are on either side of the mean.

Which of the following types of data has no measure of variability?

Nominal data

In a histogram, the proportion of the total area which must be to the left of the median is:

exactly 0.50.

In a positively skewed distribution:

the median is less than the mean.

Which of the following summary measures cannot be easily approximated from a box plot?

the standard deviation