Statistics Chapter 2 Measures of Location and Speed Flashcards
What is the mode or modal class?
The value or class that occurs most often
What is the median?
The middle value when the data values are put in order
What is the formula used to calculate the mean(non-frequency)?
X-bar = ∑x/n
What does x-bar represent?
The mean of the data
What does ∑x represent?
the sum of the data values
What does n represent?
The number of data values
What is the formula used to calculate the mean(frequency)?
X-bar = ∑xf/∑f
What does ∑xf represent?
The sum of the products of the data values and their frequencies
What does ∑f represent?
The sum of the frequencies
What is the lower quartile?
One-quarter of the way through the data set
What is the upper quartile?
Three-quarters of the way through the data set
What are percentiles?
Percentiles split the data set into 100 parts. The 10th percentile is 1/10th of the way through the data
How do you find the lower quartile for discrete data?
Divide n by 4. If this is a whole number, the lower quartile is halfway between thus data point and the one above. If it is not a whole number, round up and pick this data point
How do you find the upper quartile for discrete data?
Find 3/4 of n. If this is a whole number, the upper quartile is halfway between this data point and the one above. If it is not a whole number, round up and pick this data point
What do you assume when you interpolate?
That the data values are evenly distributed within each class
How do you calculate quartile for grouped continuous data or data presented in a cumulative frequency table?
Q_1 = n/4th data value
Q_2 = n/2th data value
Q_3 = 3n/4th data value
What is the range?
The difference between the largest and smallest values in the data set
What is the interquartile range?
The difference between the upper quartile and the lower quartile
What is the interpercentile range?
The difference between the values for two given percentiles
What are measures of spread sometimes called?
Measures of dispersion or measures of variation
How do you calculate variance(non-frequency)?
∑x^2/n - (∑x/n)^2
How do you calculate standard deviation(non-frequency)?
The standard deviation is the square root of the variance:
√ ∑x^2/n - (∑x/n)^2
How do you calculate variance and standard deviation(frequency)?
Variance = ∑fx^2/∑f - (∑fx/∑f)^2
Standard deviation = √variance
How do you find the mean of coded data? (If data is coded using the formula y=x-a/b)
Y-bar = x-bar - a/b
How do you find the standard deviation of coded data? (If data is coded using the formula y=x-a/b)
Standard deviation of y = standard deviation of x / b
