Exam 4: Summarizing Data: Variability

A researcher computes the definitional formula for SS,as finds that ∑(x-M)= 112.If this is a sample of 20 scores,then what would the value of population variance be using the computational formula?

All other things being equal,the value in the numerator is computed the same for sample variance and population variance.

A main disadvantage of computing a range is that it takes into consideration only two values regardless of the number of scores in a distribution.

Why is it important to divide by df to compute sample variance?

A(n)________ is a sample statistic that equals a population parameter on average.

A researcher records the sound (in decibels)during a series of lessons taught by a substitute teacher at a local elementary school.In his study,he found that the sound was 80±6 (M±SD)decibels.Assuming the data are normally distributed,which of the following is an appropriate conclusion?

The sample variance is an unbiased estimator of the population variance when we divide SS by df.

The sample variance will be larger than the population variance for the following data: 3,5,4,7,3,5,4,8,and 9.

For a set of data that is normally distributed with 32±4 (M±SD),we know that 68% of the data will fall between scores of 28 and 36.

If SS = 50 for a data set of 10 scores in a population,then the standard deviation is equal to 5.0.

The interquartile range and semi-interquartile range are the same measure.

A researcher records the following data: 4,4,4,4,and 3.How would you describe the variability of these data?

A researcher records the following motor assessment scores for two samples of athletes.Which sample has the largest standard deviation? Sample A: 8,10,12,15,and 18 Sample B: 16,18,20,23,and 26

The variance and standard deviation can never be

A psychologist treats 16 patients and records the number of sessions required to complete a behavioral therapy treatment for each patient.She computes SS = 800.Assuming the 16 patients constitute all patients under her care (so the population of her patients),what is the standard deviation for these data?

The SIQR can be defined as

Which of the following is a property of the standard deviation?

Which of the following is consistent with the empirical rule?

As a general rule,an interquartile range is a better estimate of variability than the IQR.

The definitional formula ______ the computational formula for SS.