chapter 4

features of a scatter diagram

- graphical technique used to show the relationship between two variables measured with interval or ratio scales - needs two variables to be drawn - one variable on the horizontal axis (x axis) - other on vertical (y axis) - each paired observation is represented by a single dot

Which of the following are features of a dot plot?

- summarizes the distribution of one variable by stalking dots at points on a number line that shoes the value of variable. the dot plot shows all values - A horizontal line indicating the possible values of the data. - One dot for each observation. - Dots "piled up" for observations very close together.

What is the function of "quartiles"?

To divide a set of observations into four equal parts

The interquartile range is a measure of dispersion usually used along with the median. What is the definition of interquartile range?

The distance between the first and third quartile.

Suppose a given data set has the following characteristics: Minimum value: 120 Q1: 160 Q2: 190 Q3: 200 Maximum Value: 220 Which of the following is true about the distribution of the data?

The distribution is negatively skewed.

contingency table

a table used to classify sample observations according to two identifiable characteristics

know the different shapes of skewness

in screenshots

pearsons coefficient of skewness

sk= 3( x with line on top - median) /s

Software Coefficient of Skewness

sk=n/(n−1)(n−2)[Σ(x−x9with line)/s)^3]

what is a measure of position

the mean 75th decile first quartile (the distance between the second and third quartile)

What is the measure of position called below which 75% of the observations occur?

the third quartile

Deciles

values of an order (min to max) data set that divide the data into 10 equal parts

percentiles

values of an ordered (min to max) data set that divide the data into 100 intervals

Quartiles

values of an ordered (min to max) data set that divide the data into four intervals

For the following ordered set of data, find the 90th percentile. 0, 2, 3, 5, 5, 6, 8, 10, 10, 11, 12, 14, 16, 20, 23

21.2 Reason: L90= (15 + 1) 90/100 = 14.4 The 90th percentile is 40% of the way from the 14th observation to the 15th observation. 20 + .4(23-20) = 21.2

For the following ordered set of data, find the 25th percentile. 0, 0, 2, 3, 5, 5, 6, 7, 7, 8, 9, 10, 11, 13, 14

3 Reason: L25= (15 + 1) 25/100 = 4 Locate the fourth value in the ordered array.

What would the location of the 83rd percentile be for a data set with 40 observations?

34.03 = (40 + 1)(83/100)

box plot

A graphic display that shows the general shape of a variable's distribution. It is based on five descriptive statistics: the maximum and minimum values, the first and third quartiles, and the median.

Which one of the following pairs of variables would be best-suited for a contingency table?

Favorite Color and Gender

Location of a percentile formula

L v p = (n +1) p/100

Contingency tables are used for summarizing data of what level?

Ordinal Nominal