Exam 3: Measures of Variability

The standard deviation must always be calculated with reference to the

The standard deviation of any distribution must always equal one-sixth of the range.

If two distributions have the same mean, then they must also have the same

The standard deviation may only be computed with reference to the mean.

If 50% of the cases fall above a given point, then 50% must also fall

The Children's Depression Inventory (CDI), developed from Beck's Depression Inventory is a self-report instrument with 27 sets of statements. Higher scores indicate higher levels of depression. Scores above 13 are said to indicate a Major Depressive Disorder (MDD) and few false positives have been reported. A random sample of 20 fifth grade students was selected and given the test. Their scores were as follows: 9,10,11,9,8,9,17,2,7,11,6,12,9,10,9,9,8,10,14,1. -What percentage of the group scored in the danger zone (13 or above)?

For the following, use SPSS: A forensic psychologist was hired to test a group of police recruits and weed out those who might have any anti-social tendencies. The psychologist chose to test them on the MMPI2 and use their scores on the ASP Scale (Anti Social Practices) to identify any possible problems among the group. Their scores were as follows: 50,53,53,47,48,55,44,46,47,45,68,43,50,51. -Find the mean

A group of inmates at a State House of Correction were tested during orientation on the LSI (Level of Security Inventory) to assess their possible security risk while incarcerated. Their scores were as follows: 4,8,2,4,6,5,7,3,4,6,5,7,4,5,4,3,7,6,5,5. -Find the mean

If the value of the standard deviation is greater than the value of the range, then

The higher the value of the standard deviation, then the more the scores are spread out around the mean.

Two distributions may have the same mean, and yet have different standard deviations.

The interquartile range lies between

A researcher gives IQ tests to a large group of adults, and discovers that the mean, median and mode all equal 100. The highest score in the group was 130 and the lowest was 70. Between IQ's of 75 and 125, 80% of the group was found, and 50% were found between IQ's of 90 and 110. The shape of the graphed distribution was mesokurtic. -The interquartile range was equal to

The Children's Depression Inventory (CDI), developed from Beck's Depression Inventory is a self-report instrument with 27 sets of statements. Higher scores indicate higher levels of depression. Scores above 13 are said to indicate a Major Depressive Disorder (MDD) and few false positives have been reported. A random sample of 20 fifth grade students was selected and given the test. Their scores were as follows: 9,10,11,9,8,9,17,2,7,11,6,12,9,10,9,9,8,10,14,1. -If the distribution had been absolutely normal, what standard deviation (standard value) would you have predicted for a group of scores with this range value?

The difference between the highest and lowest scores in any distribution is called

A score which is at the 95th percentile must exceed

The Children's Depression Inventory (CDI), developed from Beck's Depression Inventory is a self-report instrument with 27 sets of statements. Higher scores indicate higher levels of depression. Scores above 13 are said to indicate a Major Depressive Disorder (MDD) and few false positives have been reported. A random sample of 20 fifth grade students was selected and given the test. Their scores were as follows: 9,10,11,9,8,9,17,2,7,11,6,12,9,10,9,9,8,10,14,1. -In comparing your predicted value with the actual value for the standard deviation, what conclusions might you draw regarding the shape of the distribution.

You know you've made a math error whenever the standard deviation is

Kurtosis refers to the flatness or peakedness of the curve.

A researcher wished to evaluate the operating life of a certain brand of storage battery. A group of 30, brand-new batteries was selected and placed in 30 identical automobiles. The lights in each automobile were then turned on (without running the engines), and the length of time before the batteries were fully discharged (lights went out) was recorded. The scores, in hours, were: 15, 10, 20, 18, 18, 11, 11, 11, 11, 12, 12, 12, 10, 9, 9, 8, 9, 9, 11, 11, 11, 15, 12, 12, 12, 10, 12, 12, 15, 12. -Calculate the mode.