Statistics: Section 2.2
The _________________ is the difference between consecutive lower class limits.
class width
Classes
are categories into which data is grouped.
Histogram
is constructed by drawing rectangles for each class of data. The height of each rectangle is the frequency or relative frequency of the class. The width of each rectangle is the same and the rectangles touch each other.
Select the correct choices that complete the sentence below. The ______ class limit is the smallest value within the class and the ______ class limit is the largest value within the class.
lower;upper
Class width
the difference between consecutive lower class limits Class width= largest data value-smallest data value/number of classes
Uniform distribution
the frequency of each value of the variable is evenly spread out across the values of the variable. The histogram down the middle, right, and left sides are symmetrical
Bell shaped distribution
the highest frequency occurs in the middle and frequencies tail off to the left and right of the middle ( the graph looks like a profile of a bell)
Time series plot
Obtained by plotting the time in which a variable is measured on the horizontal axis and the corresponding value of the variable on the vertical axis. Line segments are then drawn connecting the points.
Upper class limit
the largest value with thin the class
Lower class limit
the smallest value with thin the class
Skewed left
the tail to the left of the peak is longer than the tail to the right of the peak
Skewed right
the tail to the right of the peak is longer than the tail to the left of the peak
Time series data
the value of a variable is measured at different points in time
For IQ scores of students, state whether you would expect a histogram of the data to be bell-shaped, uniform, skewed left, or skewed right.
Bell shaped
Steam and leaf plot
Is another way to represent quantitative data graphically
To predict future enrollment in a school district, fifty households within the district were sampled, and asked to disclose the number of children under the age of five living in the household. The results of the survey are presented in the table. Complete parts (a) through (c) below.
(a) Construct a relative frequency distribution of the data. Number of Children under 5 Relative Frequency 0 0.28 1 0.3 2 0.28 3 0.1 4 0.04 (b) What percentage of households has two children under the age of 5? 28% c) What percentage of households has one or two children under the age of 5? 58%
Why shouldn't classes overlap when summarizing continuous data in a frequency or relative frequency distribution?
Classes shouldn't overlap so there is no confusion as to which class an observation belongs.
Open ended
if the first class has no lower class limit or the last class has no upper class limit