The weighted mean is used for what data?

ordinal

What is the F_j in the weighted mean formula?

Frequency of the specific class

What is X_j in the weighted mean formula?

the midpoint/average of each class interval

How to calculate the weighted mean :

1. Find the average/midpoint for each class
2. then multiply the class frequency by the class average for EACH CLASS = X_j * F_j
3. Add together  X_j * F_jof each class
4. Divide the sum of X_j * F_j of each class by sum of the frequencys of all the classes

What factor determines the appropriate measure of central tendency?

the symmetry of the data/ frequency distribution

What is a normal (symmetrical) frequency distribution?

THe values of your data set are distributed fairly evenly on both sides of the mean of the data

Where is the mode, median, and mean located on the distribution curve?

Center of a distribution curve

What is a skewed distribution?

The data values are distributed unevenly on both sides of the mean of the data

What is a positive skew?

The greatest frequency of the data occurs toward the low end of the range

The mean of the data values is pulled away from the area of the greatest frequency toward the right (positive) direction of the x-axis by a few high values in the data set

What is a negative skew?

The greatest frequency of the data occurs toward the high end of the range

The mean of the data is toward the left (negative)

What measures of central tendency can be used for a normal distribution?

ALL  THREE--mode, median, mean

What measures of central tendency can be used for a skewed distribution?

Mode and Median

What measures of central tendency can be used for an extremely skewed distribution and bimodal?

Mode

What do measures of dispersion and variability tell you?

They provide an indication of the degree to which data values are distributed to either side of their mean

What is the range?

The difference between the largest and smallest data values

What is standard deviation?

Based on individual deviations of each data value in a data set from their mean

Sample Standard Deviation

Population Standard Deviation

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What is the coefficient of variation?

In what circumstances should the coefficient of variation be used?

1. When comparing standard deviations between geographic regions
2. When comparing the standard deviations of two or more variables with different measurement units
3. when comparing the standard deviation of two or more variables whose data values are significantly different in magnitude

Coefficient of Variation (sample) Formula

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Coefficient of Variation (population) Formula

If Pearson's R is statistically significant

if we can rely on pearsons r

Pearsons R

Correlation Coefficient Formula

Degrees of freedom

 One degree of freedom is subtracted for each variable

1. Calculate pearsons r
2. Calculate t-test
3. Use t-test and degrees of freedom to find the critical value
4. Compare the t-test to the critical value: must be equal to or greater than the critical value

Coefficient of Determination Formula

coefficient of determination = r² * 100