Chapter 2 terms and HW questions

It has a normal distribution if

1. The frequencies start low, then increase to one or two high frequencies, and then decrease to a low frequency 2. The distribution is approximately symmetric

​_______ are sample values that lie very far away from the majority of the other sample values.

outliers

When drawings of objects are used to depict​ data, false impressions can be made. These drawings are called​ _______.

pictographs

Time-series graph

represents data that occur over a specific period of time

A​ _______ is a plot of paired data​ (x,y) and is helpful in determining whether there is a relationship between the two variables.

scatterplot

A histogram aids in analyzing the​ _______ of the data.

shape of distribution

Class midpoints

the values in the middle of the classes

The bars in a histogram​

touch

The sum of percentages in a relative frequency distribution must be

very close to 100%, 99% or 101% is acceptable

Listed below are body temperatures ​(°​F) of healthy adults. Why is it that a graph of these data would not be very effective in helping us understand the​ data? 98.6 98.6 98.0 98.0 99.0 98.4 98.4 98.4 98.4 98.6

The data set is too small for a graph to reveal important characteristics of the data.

Bar graphs

bars of equal width to show frequencies of categories or qualitative data

The heights of the bars of a histogram correspond to​ _______ values.

frequency

A​ _______ histogram has the same shape and horizontal scale as a​ histogram, but the vertical scale is marked with relative frequencies instead of actual frequencies.

relative frequency

In a​ _______ distribution, the frequency of a class is replaced with a proportion or percent.

relative frequency

Frequency distribution (frequency table)

shows how data are partitioned among several categories (or classes) by listing the categories along with the number (frequency) of data values in each of them

pictographs

simple drawings that look like the objects they represent, often misleading and shouldn't be used

Graphs can be deceptive by not

starting at 0!

The presence of gaps can suggest

that the data are from two or more different populations

Class width

the difference between consecutive lower class limits = (Max data value - min data value) / number of classes Round up

Cumulative frequency distribution

the frequency for each class is the sum of the frequencies for that class and all previous classes

Upper class limits

the largest numbers that can belong to each of the different classes

Frequency for a particular class

the number of original values that fall into that class

class boundaries

the numbers used to separate the classes, but without the gaps created by class limits

Lower class limits

the smallest numbers that can belong to the different classes

stemplot/stem-and-leaf plot

Represents quantitative data by separating each value into two parts: the stem (such as the leftmost digit) and the leaf (such as the rightmost digit)

A​ _______ helps us understand the nature of the distribution of a data set.

frequency distribution

​A(n) _______ uses line segments to connect points located directly above class midpoint values.

frequency polygon

Relative frequency histogram

has the same shape and horizontal scale as a histogram, but the vertical scale is marked with relative frequencies instead of actual frequencies

Frequency polygon

line segments connected to points located directly above class midpoint values

Pareto chart

A bar graph for categorical data, with the added stipulation that the bars are arranged in descending order of frequencies (decrease in height form left to right)

Features of a Dotplot

- displays the shape of distribution of data - it is usually possible to recreate the original list of data values

Features of a stem plot

- shows the shape of the distribution of the data - retains the original data values - the sample data are sorted (arranged in order)

Important uses of a histogram

-Visually displays the shape of the distribution of the data -Shows the location of the center of the data -Shows the spread of the data -Identifies outliers

Dotplot

A graph of quantitative data I which each data value is plotted as a point (or dot) above a horizontal scale of of values.

skewed left (negatively skewed)

A histogram with a long left-hand tail

Pie chart

Depicts categorical data as slices of a circle

Relative frequency distribution (percentage frequency distribution)

Each class frequency is replaced by a relative frequency (or proportion) or a percentage Frequency for a class / sum of all frequencies (x100 if looking for %)

If we have a large voluntary response sample consisting of weights of subjects who chose to respond to a survey posted on the​ Internet, can a graph help to overcome the deficiency of having a voluntary response​ sample?

No, a graph cannot help to overcome the deficiency. If the sample is a bad​ sample, there are no graphs or other techniques that can be used to salvage the data.

If we collect a large sample of blood platelet counts and if our sample includes a single​ outlier, how will that outlier appear in a​ histogram?

The outlier will appear as a bar far from all of the other bars with a height that corresponds to a frequency of 1.

normal distribution on quantile plot

The pattern of the points is reasonably close to a straight line and dont show a systematic pattern

Which of the following is NOT true about statistical​ graphs?

They utilize areas or volumes for data that are​ one-dimensional in nature.

Histogram

a graph consisting of bars of equal width drawn adjacent to each other. The horizontal scale represents classes of data values, and the vertical scale represents frequencies.

skewed right (positively skewed)

a histogram with a long right-hand tail

In a​ graph, if one or both axes begin at some value other than​ zero, the differences are exaggerated. This bad graphing method is known as​ _______.

a nonzero axis