PS341
When an event cannot occur, it's probability value is_____.
0
What % of scores lie above Z score -3?
0.13%
When an event must occur, it's probability value is ____.
1.00
What % of scores lie between Z scores -1 and -2?
13.59%
-1 Z score = ____%ile
16th %ile
What % of scores lie between Z scores +2 and +3?
2.14%
The more frequently an event occurs, the higher is it's probably of occurrence
False
The ratio s/t defines what important statistical concept?
Probability
To find the probability of selecting one event and another, the separate probabilities should be multiplied.
True "Multi - and"
For a normal distribution, 50% of the Z scores must be positive.
True 50% are above and 50% are below 0 the mean Z score.
A Z score of zero always indicates that the raw score coincides with the mean.
True
Normal distributions must always be unimodal
True
A positive z score always yields a percentile rank above 50.
True 50th percentile is the middle of the curve. Z score of 0 T score of 50 IQ score of 100
Between Z scores of +/- 3.00 under the normal curve can be found almost the entire distribution.
True 99.74% of cases fall between +/- 3.00
-2 Z score = ____%ile
2nd %ile
What % of scores lie between Z scores 0 and +1?
34.13%
0 Z score = _____%ile
50th %ile
0 Z score = _____ %ile
50th percentile
What % of cases fall between Z scores of +/- 1.00?
68.26%
+1 Z score =_____%ile
84th %ile
What % of cases fall between Z scores of +/- 2.00?
95.44%
+2 Z score =_____%ile
98th %ile
What % of cases fall between Z scores of +/- 3.00?
99.74%
The standard deviation of the T score distribution must equal the standard deviation of the raw score distribution.
False
All unimodal distributions are normal.
False Just because it is unimodal doesn't mean that it isn't skewed.
A negative Z score must yield a negative probability value.
False Probability cannot be a negative number
In a normal distribution, it is sometimes possible for the mean to occur above the 50th percentile
False That would not be a normal distribution, it would be skewed.
An individual score at the 10th percentile is among the top tenth of the distribution.
False The top tenth of the distribution would be the 90th percentile.
A negative z score always yields a negative percentile.
False You cannot have a negative percentile
If a given event occurs at a frequency of 50%, it's probability of occurrence is 0.50
True
Probability values can never exceed 1.00
True
To find the probability of selecting one event or another, the separate probabilities should be added
True "Add - or"
A negative Z score always indicates that the raw score is below the mean.
True Mean Z score is 0, so negative scores would be below the mean.
If the Z score is zero, the T score must be 50.
True 50 = mean T score
A T score of less than 50 must yield a negative Z score
True 50 T score = 0 Z score
All T scores greater than 50 must yield percentiles that are greater than 50.
True 50 T score = 50th percentile
If the mean of a set of normally distributed values is 11.83, the median is also equal to 11.83.
True Mean=Mdn=Mo in a normal distribution
