Psy230 Ch1 Test
Which of the following z scores represent(s) the most extreme value in a distribution of scores assuming they are normally distributed?
-3.12
In a normal distribution the z score for the mean equals ________.
0
The mean of the z distribution equals ________.
0
The standard normal curve is symmetrical about-
0
∑(X-X-)=
0
The proportion of scores less than z = 0.00 is
0.50
The standard deviation of the standard normal distribution equals ______.
1
A standardized test has a mean of 88 and a standard deviation of 12. What is the score at the 90th percentile? Assume a normal distribution.
103.36
On a test with a population mean of 75 and standard deviation equal to 16, if the scores are normally distributed, what is the percentile rank of a score of 56?
11.70
If s = 12 for a set of 200 scores and 5 points are subtracted from each of the scores, the value of the standard deviation would be:
12
What is 17.295 rounded to one decimal place?
17.3
What is the percentile rank of a z score of -0.47?
31.92
If the range of a distribution were 89 and the data were reported as whole numbers, what would the width of the class interval be if one chose to group the distribution into approximately 10-20 class intervals?
5 (need evenly divisible lower apparent limits)
What are the real limits of the observation of 6 seconds (measured to the nearest second)?
5.5-6.5
The range of a set of scores with a maximum value of 92 and a minimum value of 26 is ________.
66
Ιn a normal distribution approximately ___ of the scores will fall within 1 standard deviation of the mean.
68%
Variance
A measure of spread within a distribution (the square of the standard deviation).
The Standard Normal Curve
A normal distribution with mean of zero and standard deviation of one. Probabilities are given in Table A for values of the standard Normal variable.
The symbol "∑" means: ________.
Add the scores
When individual scores are combined into groups, ________
Information is lost and a meaningful visual display can result depending on the interval width.
x-
Mean of a sample
µ
Mean of population
The mean is ________ sensitive to extreme scores than the median.
More Sensitive
If a distribution of raw scores is negatively skewed, transforming the raw scores into z scores will result in a ________ distribution.
Negatively skewed distribution
Classifying subjects on the basis of sex is an example of using what kind of scale?
Nominal
The purpose of a frequency distribution is to ______.
- present scores and their frequency distribution of occurrence -presents data in a more meaningful way than single scores
σ
Standard deviation of a population
s
Standard deviation of a sample
∑(X-X-)^2 is called ________.
Sum of Squares
A fundamental property of a nominal scale is equivalence.
True
If a curve is negatively skewed, most of the scores occur at the higher values and the curve tails off toward the lower end of the horizontal axis.
True
In grouping scores, the wider the intervals, the more information that is lost.
True
It is possible to have a set of scores with three different values for central tendency.
True
Measurement is always approximate with a continuous variable.
True
The area under the normal curve represents the proportion of scores that are contained in the area.
True
The percentile rank of a score is equal to the percentage of scores in the distribution that fall at or below the score in question.
True
We use N- 1 in the denominator of the equation for calculating the sample standard deviation because it provides us with a more accurate estimate of the population standard deviation.
True
When constructing bar graphs, the bars do not touch each other because ________.
it emphasizes the lack of quantitative relationship between the categories
In a negatively skewed distribution, the mean will generally be ______ the median.
less than
Standard Scores
number of standard deviations by which the value of a raw score (i.e., an observed value or data point) is above or below the mean value of what is being observed or measured. Raw scores above the mean have positive standard scores, while those below the mean have negative standard scores.
Mode
value that appears most often in a set of data.
Would you rather have an income (assume a normal distribution and you are greedy) ________?
with a Z score of 1.96
The z distribution takes on the same shape as the raw scores.
true
The number of students in a class is an example of a continuous variable.
False
∑X 2and (∑X) 2generally yield the same answer.
False
What levels of measurement are discrete vs continuous? Which could be either?
Discrete variables reflect ordinal and integer values, which are negative or positive whole numbers. Continuous variables reflect partial numbers in the form of fractions or decimals.
Any percentile point for a distribution of scores must have a value equal to one of the scores.
False
For data that are not normally distributed, the standard deviation will sometimes be negative.
False
It is impossible to have a z score of 30.2.
False
What types of variables are likely to be normally distributed?
Height, birth weight, reading ability, job satisfaction, or SAT scores. Consistent growth.
Range
The lowest and highest scores.
Using an ordinal scale to assess leadership, which of the following statements is appropriate?
Y has the most leadership ability
Standard Deviation
a measure that is used to quantify the amount of variation or dispersion of a set of data values.
Identify the level of measurement for: a. the gender of a child b. a person's religion c. a student's class rank d. an attitude score on a prejudice inventory e. the time required to complete a task f. the rating of a task as either "easy," "mildly difficult," or "difficult"
a. nominal b. nominal c. ordinal d. interval e. ratio f. ordinal
Mean
average of scores: add up all of the scores and divide by the number of scores.
What indicates the number of scores that fell below the upper real limit of each interval?
cumulative frequency distribution
Number of bar presses is an example of a(n) _____ variable
discrete
σ^2 (sigma squared)
population variance
A distribution which has a predominance of scores at the lower values of the distribution and which tails off at the higher end is _______.
positively skewed
The number of legs on a centipede is an example of a(an) ________ scale.
ratio
What indicates the proportion of the total number of scores which occurred in each interval?
relative frequency
Σ(X-X)2 is called _________.
sum of squares
The z-score (or standard score) is defined as
the distance of a raw score from the mean in standard deviation units - transformed raw score
Median
the midpoint of a frequency
The z-score (or standard score) is defined as
the number of standard deviation from the mean
If 5 points are added to each score in a distribution -
the standard deviation will be unchanged
Consider a distribution with N=100, X = 50, and Σ(XX)2 = 9875. If 10 new scores of 50 were added to the distribution, what would happen to the sum of squares?
the value would remain unchanged.
For any z distribution of normally distributed scores, P50 is always equal to zero.
true
What is the appropriate symbol for the formula
σx
