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45 Cards in this Set
 Front
 Back
measures of central tendency

also called measures of average
mean median mode midrange 

measures of variation

also called measures of dispersion
range variance standard deviation 

measures of position

used extensively in psychology and education, norms
percentiles deciles quartiles 

parameters

a characteristic or measurement obtained by using all data for a population


statistic

a characteristic or measure obtained using data values from a sample


what is the general rounding rule?

rounding should not be done until the final answer is calculated


mean
formula 
also known as the arithmic average
add all values then divide by the number of values 

mean

also known as the arithmic average
add all values then divide by the number of values 

rounding rule for the mean

the mean should be rounded to one more decimal place than occurs in the raw data


median

the midpoint of the data array


data array

ordered data
1 2 3 4 5 12 23 32 44 51 

mode

the value that occurs most often in a data set
there can be one, none, or multiple modes a data set w/ multiple modes is bimodal 

the modal class

the class with the largest frequency


midrange
formula 
a rough estimate of the middle
(lowest value + highest value) / 2 

midrange
formula 
a rough estimate of the middle
(lowest value + highest value) / 2 

weighted mean
formula 
used when values are not equally represented
multiple each value by its corresponding weight, divide the sum of products by the sum of weights 

which varies less,
mean, median or mode? 
mean varies the least of these


Can a mean be computed for an open ended frequency distribution?

no


what are outliers?

extremely high or low values that can affect the accuracy of the mean and the midrange


can the median be used for open ended distributions?

yes


positively skewed distribution

right skewed tail to the right


symmetric distribution

data is evenly distributed on both sides of the mean


negatively skewed

left skewed, tail to the left


measurements for the spread of variability

range
variance standard deviation 

rounding rule for standard deviation

final answer should be rounded to one more decimal place that the original data


variance
formula 
is the average of the squares of the distance each value is away from the mean
subtract the mean from each value, square each difference, add all squared differences, divide the sum of squared differences by the population size 

the larger the variance or standard deviation,...

the more variable the data


the symbol for sample size is

n


the symbol for an individual value is

x


the symbol for range is

R


how do you find the standard deviation?

take the square root of the variance


the symbol for the population standard deviation is

ó


the symbol for the population standard deviation is

ó


the symbol for population mean is

µ


the symbol for sample mean is

X (with a bar above it)


the symbol for a sample standard deviation is

s


Chebyshev's theorem states that for any distribution___________________ of the data will fall within 2 standard deviations of the mean.

75%


coefficient of variation formula

standard deviation divided by the mean and expressed a percentage


symbol for coefficient of variation

CVar


the empirical rule

these are true with a normal distribution
1)appr. 68% of data values will fall within 1 standard deviation of the mean 2) 95% will fall within 2 3) 99.7% will fall within 3 

z score
formula 
also called standard score
the number of standard deviations a number is from the mean (valuemean)/ standard deviation 

percentile
formula 
[(number of values below x)+ .5] /total # of values, given as a percentage


deciles

divide the distribution into 10 groups


find outliers

Q1[(Q3Q1)*1.5]
and Q3+[(Q3Q1)*1.5] 

interquartile range

Q3Q1
