PSY 2310: Module 6
What symbol represents the standard deviation of a population?
σ
Use the SPSS printout below to identify the standard deviation for typical salaries of a sample of 10 states: $70,000; $41,400; $46,700; $38,800; $55,400; $62,800; $53,200; $41,100; $69,800; and $62,900.
$11,897.47
Compute the variance for this sample of 8 scores: 3, 3, 2, 4, 5, 1, 9, 8.
. 7.98
If all scores in a data set have the same value, what will the standard deviation equal?
0
The smallest standard deviation that is possible is __________ because this would mean that __________.
0; all of the scores are the same
Using the following SPSS output, what is the standard deviation of these data?
2.08
What is the SD2 value reported in this table?
2.33
Compute the standard deviation for this population of scores: 3, 3, 2, 4, 5, 1, 9, 8, 5, 7.
2.49
Compute the standard deviation for this sample of 8 scores: 3, 3, 2, 4, 5, 1, 9, 8.
2.83
The following table is an SPSS output a statistics instructor created. The instructor was measuring students' attitudes about how well prepared students felt entering the statistics course. The students filled out a questionnaire with six questions, answering Yes or No to each question. The possible scores ranged from 0 (all "No" reponses) - indicating not feeling prepared at all, to 6 (all "Yes" responses) - feeling prepared for the class. How many students completed the questionnaire? Statistics Prep_Score N Valid 20 Missing 0 Mean 3.8320 Median 3.0000 Mode 3.00 Std. Deviation 1.52467 Variance 2.325 Minimum .00 Maximum 6.00
20
What was the most common score on the preparedness questionnaire?
3
What is the average preparedness score?
3.83
Identify the mode for this data set.
4
Identify the median for this data set.
4.5
Compute the variance for this population of scores: 3, 3, 2, 4, 5, 1, 9, 8, 5, 7.
6.21
What characteristic of a distribution of scores does a standard deviation describe?
All of the above
The definitional method for finding the SS and the computational method for finding the SS will always provide the same value, but in most situations the __________ method is faster and will not produce rounding error.
computational SS =Σx2 - (Σx)2 /N
In order for two data sets to have the same standard deviation, they must have the same mean.
False
When estimating the variance of a population from a sample, you are performing __________ so divide the SS by __________.
Inferential statistics, N-1
Why is the range a poor measure of variability?
It uses only two values rather than all of the values in the distribution.
Based on the location of the mean, median, and mode identify the shape of the distribution.
Positively skewed
What measure of variability should be used when the data are ordinal?
Range
What symbol represents the standard deviation of a sample?
SD
Which equation is used for computing the SS?
SS=Σx2 - (Σx)2 /N
Identify the statement that best represents an APA format report of the results.
The average number of incorrect answers on the exam for the statistics course is M = 5.81, and the average distance of scores from the mean is SD = 2.90 points.
A deviation score measures __________.
The distance of an individual score from the mean.
When computing the variance of an entire population, you are performing __________ so divide the SS by __________.
descriptive statistics, N
SPSS can only be used to compute the standard deviation of a sample, not a population.
True
The SS is computed in exactly the same way for a sample and a population.
True
When computing the standard deviation we must first subtract the mean from each score. This difference is called __________.
a deviation score
Which equation defines the sum of squared deviation scores?
Σ /x−μ / ^2
When you are using a sample to estimate a population's standard deviation, you are doing __________ statistics.
inferential
When computing a sample's standard deviation, there __________ to the computation process relative to when you are computing a population's standard deviation.
is one change
Which measure of variability describes the typical distance of scores from the mean?
ordinal
Which measure of variability describes the typical distance of scores from the mean?
standard deviation
SS stands for the __________.
sum of the squared deviation scores
When computing the standard deviation, SS stands for __________.
sum of the squared deviation scores
The standard deviation (σ) is __________.
the typical distance of all the scores from the mean; some scores will be further away and some closer, but this is the typical distance
We divide SS by N-1 when computing the sample variance.
true
The variance (σ2) is the __________.
typical squared deviation from the mean
When using a sample to estimate a population's variability, the SS is divided by N-1 rather than by N to correct for a sample's tendency to __________.
underestimate the variability of a population
Statisticians square each deviation score so that __________.
when they sum them they will not sum to zero
