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