Statistics 120 2:2

Contrast the differences between histograms and bar graphs.

Histograms are for quantitative data while bar graphs are for qualitative data. Also, bars in a histogram can touch each other, whereas the bars in a bar graph will have gaps between them.

Why shouldn't classes overlap when one summarizes continuous data?

If classes overlap, then some observations will be counted in more than one class. This means that certain observations will end up in more than one bar of a histogram, which will misrepresent the data!

Difference Between Rounding UP and Rounding OFF

In Other Words page. 87 Rounding up is different from rounding off. For example, 6.2 rounded up would be 7, while 6.2 rounded off would be 6.

see book p. 94-6 The histogram to the right represents to total rainfall for each time it rained in Chicago during the month of August since 1871. The histogram was taken from the Chicago Tribune on August 14, 2001. What is wrong with the histogram?

One problem with this histogram is that the classes have different widths. For example, the first class goes from .1 to .49 (width of .39) and the second class goes from .5 to .99 (width of .49). Other problems with this histogram are that there are no axis labels and there is no scale on the y-axis. and there is no label to describe data for x axis

State the advantages and disadvantages of histograms versus stem and leaf plots

You can actually tell what the exact data are by looking at a stem & leaf plot, whereas with a histogram you can't tell what the exact data are. An advantage of a histogram is that it provides a summary of the number of responses in each class.

A frequency distribution lists the ___ of each category of data, while a relative frequency distribution lists the ___ of occurrences of each category of data.

A frequency distribution lists the number of occurrences of each category of data, while a relative frequency distribution lists the proportion (or percent) of occurrences of each category of data.

True or False: When taking a systematic random sample of size n, every group of size n from the population has that same chance of being selected.

False

P 94 question 10 10. True or False: The shape of the distribution shown is best classified as uniform.

False Symmetrical

Page 94 question 9 True or False: The shape of the distribution shown is best classified as skewed left.

False - Skewed Right

8. True or False: Stem-and-leaf plots are particularly useful for large sets of data.

False - Stem-and-Leaf Plots lose their usefullness when data sets are large or when they consist of a large range of values. Sometimes the steps to create a Stem-and-Leaf Plot has to be modified to meet the needs of the data. You can gather the raw data from a Stem-and-Leaf Plot **Once a frequency distribution or histogram of continuous data is created, the raw data are lost. However, you can retrieve the raw data from a Stem-and-Leaf Plot

If a data set contains 10,000 values arranged in increasing order, where is the median located?

The median would be the average of the 2 middle values once the data is ordered. This would be the average of the 5000th observation and the 5001st observation.

7. True or False: There is not one particular frequency distribution that is correct, but there are frequency distributions that are less desirable than others.

True p. 86 Creating the classes for summarizing continuous data is an art form. There is no such thing as the correct frequency distribution. However, there can be less desirable frequency distributions. The larger the class width, the fewer classes a frequency distribution will have.