Stat121 Lesson 6

Why does this histogram represent a distribution?

A distribution gives a list of the possible values of the variable together with how often each value occurs. This histogram does both.

Shape, center, and spread have no meaning on a ____ _____.

Bar graph.

Bar graph or pie chart: which one is better for statistics and why?

Bar graph. It is easier to see the differences between categories. ALso, multiple data sets can be included in a single bar graph.

What type of variable is zip code and why?

Categorical. While "zip code" is a number, average "zip code" does not make sense. So, "zip code" is categorical. Further, "zip code" describes where a person lives. A zip code of 05167 cannot be compared with a zip code of 99242.

What gives a location of the midpoint of a distribution?

Center value.

True or false: Histograms are appropriate for either categorical or quantitative data.

False.

True or false: Outliers are always miscoded data points.

False. Only some outliers are miscoded data points; many represent valid data values.

True or false: For every set of data, there is only one possible stemplot.

Observations in a data set can be displayed in two or three different stemplots.

What type of data can be displayed with a dotplot?

Quantitative data

What type of variable is hourly wage?

Quantitative. Numbers having value can be assigned to "hourly wage," so "hourly wage" is quantitative. Further, average "hourly wage" does make sense.

What graphs should be used to display the variable cholesterol levels?

Since "cholesterol level" is quantitative, a dotplot, stemplot, histogram or boxplot should be used to display these data.

What graphs should be used to display the variable number of siblings (including half and step siblings)?

Since "number of siblings" is quantitative, a dotplot, stemplot, histogram or boxplot should be used to display these data.

Which graph is best for large data sets?

Since every observation in a data set is plotted in both a dotplot and a stemplot, a histogram is best for large data sets.

What graphs should be used to display the variable method of transportation to campus?

Since the variable "method of transportation to campus" is categorical, a bar graph or pie chart should be used to display these data.

In a sewing class a teacher assigned the students to make a skirt. As part of the skirt construction, students were required to insert a zipper. In order to assess the students' sewing skills, the teacher timed how long it took each student to insert his/her zipper. Who are being studied?

Students in a sewing class. Since the teacher measured the time it took each student to insert a zipper, students are being studied.

True or false: We only use shape to describe graphs for quantitative data.

True

Referring to the previous question (sewing), why were the data collected?

The why of this study was to assess students' sewing skills.

Referring to the previous question (sewing), what is being measured?

Time to insert a zipper was measured on each student.

True or false: Bars in a bar graph should be separated by spaces.

True

True or false: Each dot in a dotplot represents a data value.

True

True or false: Spread tells us about the variability of the data in a histogram.

True

True or false: In a stemplot, a value from every observation is given as a leaf.

True.

True or false: When identifying center, one must take the heights of the bars into account.

True.

True or false: For categorical data percentages are preferred over counts for comparisons.

True. Percentages are easier to compare than counts.

True or false: Shape, center and spread are never used to describe bar charts.

True. This is a correct statement because shape, center and spread apply only to graphs displaying quantitative data.

In a stemplot, which digit is represented in the stems?

Typically, the leading digit in a number is plotted in the stems of a stemplot.

Which graphs are best for large data sets?

histograms

What type of graph should be used for categorical data? How should it be summarized?

bar graphs or pie charts. Should be summarized using percentages or counts

The label of the x axis on a bar graph is a ______________ and is categorical, while the label of the x axis on a histogram is a _________________ and is quantitative

description. number.

What type of graph should be used for quantitative data? How should it be summarized?

dotplot, stemplot, histogram, or boxplot. Should be summarized by mean, median, quartiles, standard deviation, etc.

Which graphs work well for small data sets of numbers?

dotplots and stemplots

Quantitative variables have ______________ ______________.

numerical values

What is an outlier?

observations that fall outside the overall pattern of the distribution.