Statistics Midterm 1

Standard Deviation s

E = Sum Xi= u = mean N = size of population

Frequency

How often a number occurs within the class limits

coefficient of variation

A measure of relative variability computed by dividing the standard deviation (s) by the mean (x) and multiplying by 100.

Verify that Σx^2

Add the products of each number squared

Mode

The value that occurs most frequently in a given data set

Find the class width

largest data value- smallest data value/ desired # of classes

Midpoint

lower class limit + upper class limit/ 2

Stem and leaf display

method of exploratory data analysis that is used to rank-order and arrange data into groups

Slope m

r times Sy/Sx

Cumulative relative frequency

the accumulation of the previous relative frequencies. To find the cumulative relative frequencies, add all the previous relative frequencies to the relative frequency for the current row.

Mean

the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores

Range

the difference between the highest and lowest scores in a distribution

Relative frequency

the fraction of times an answer occurs. To find the relative frequencies, divide each frequency by the total number of students in the sample

Median

the middle score in a distribution; half the scores are above it and half are below it

What is the difference between a class boundary and a class limit?

-Class limits are possible data values -Class boundaries are not possible data values. -Class limits specify the span of data values that fall within a class -Class boundaries are values halfway between the upper class limit of one class and the lower class limit of the next.

Population N

Step 1: Calculate the mean of the data—this is μ in the formula. Step 2: Subtract the mean from each data point. These differences are called deviations. Data points below the mean will have negative deviations, and data points above the mean will have positive deviations. Step 3: Square each deviation to make it positive. Step 4: Add the squared deviations together. Step 5: Divide the sum by the number of data points in the population. The result is called the variance. Step 6: Take the square root of the variance to get the standard deviation.

Verify that Σx

add numbers