Deck 6: Probability

Question 1

If an event can occur five times out of 100, its probability value is

A) .20
B) .80
C) .95
D) .05

Answer 1

D

Question 2

Probability is based on how often a given event

A) will occur out of 100
B) will occur out of 52 times
C) will occur just once
D) will not occur at all

Answer 2

A

Question 3

Odds against are based on how often a given event

A) will occur out of 100 times
B) will occur out of any number of times
C) will occur just once
D) will not occur at all, to the number of times it will

Answer 3

D

Question 4

The so-called "Gambler's Fallacy" makes the mistake of not recognizing

A) the low-probability events
B) the high-probability events
C) the independent-events situation
D) that losses occur more frequently than wins

Question 5

If the odds against an event are 5 to 1, the probability of its occurrence is

A) .17
B) .05
C) .01
D) .25

Question 6

Suppose you had flipped a fair coin 19 times and "tails" had come up each time. The probability of now tossing a "head" on the 20th flip would then be

A) .50
B) .05
C) .95
D) .99

Question 7

A probability value of .25 means that an event will occur

A) once out of 25 times
B) 25 times out of 100
C) once out of 5 times
D) 75 times out of 100

Question 8

Probability is equal to

A) s/t
B) t/s
C) odds divided by chances
D) none of these

Question 9

If the odds against an event are 19 to 1, the probability of its occurrence is

A) .17
B) .05
C) .01
D) .25

Question 10

If an event has a probability value of .95, its frequency of occurrence is

A) 5%
B) 95%
C) 19 to 1
D) 47.5%

Question 11

When events cannot influence or be influenced by other events, they are said to be

A) low-probability events
B) high-probability events
C) chance events
D) independent events

Question 12

Suppose you had flipped a coin 19 times and "heads" had come up each time. The probability of flipping a "head" on the 20th flip would then be

A) .50
B) .05
C) .95
D) .01

Question 13

If the odds against an event are 3 to 1, the probability of its occurrence is

A) .17
B) .05
C) .01
D) .25

Question 14

If an event can occur once out of 20 times, its probability value is

A) .20
B) .80
C) .95
D) .05

Question 15

When tossing coins, the frequency of occurrence of "heads" turning up is

A) .50
B) .50%
C) 1 to 1
D) 50%

Question 16

Probability is defined as

A) the number of total events over the number of chances
B) the chances an event cannot occur over the chances it can
C) the number of times a specific event will occur over thee total number of events
D) the total number of events over the number of times a specific event will

Question 17

When the frequency of an event is 75%, its probability is

A) 3 to 1
B) .25
C) .67
D) none of these

Question 18

When the frequency of an event is 95%, its probability is

A) .95
B) .05
C) .50
D) Cannot be found from the information given

Question 19

The so-called law of averages only applies

A) under controlled conditions
B) when the probabilities are conditional
C) in the long run
D) in the short run

Question 20

When the frequency of an event is 25%, its probability is

A) 3 to 1
B) .25
C) .75
D) none of these

Question 21

When combining probabilities, to find the probability of one event AND another event, the separate probabilities should be

A) multiplied
B) divided
C) subtracted
D) added

Question 22

Under the normal curve, the probability of any single score being above the 50th percentile is

A) 0
B) .16
C) .34
D) .50

Question 23

The probability of obtaining a z score of +1.00 or higher, is

A) 1.00
B) .16
C) .84
D) .34

Question 24

Under the normal curve, the probability of a score occurring below the mean is

A) .68
B) .50
C) 2 to 1
D) .68%

Question 25

Under the normal curve, the probability of a score occurring above the mean is

A) .68
B) .50
C) 2 to 1
D) .68%

Question 26

Under the normal curve, the probability of a score occurring within one standard deviation (plus or minus) of the mean is

A) .68
B) .50
C) 2 to 1
D) .68%

Question 27

No probability value may ever be less than

A) 1.00
B) .99
C) 0
D) there is no upper limit to the size of a given probability value

Question 28

When an event must occur, its probability value is

A) .99
B) 1.00
C) 0
D) 100%

Question 29

When an event cannot occur, its probability value is

A) .99
B) 1.00
C) 0
D) 100%

Question 30

The use of z scores for obtaining probabilities is only possible when

A) the events are independent
B) the probabilities are conditional
C) the distribution curve is symmetrical
D) the distribution curve is normal

Question 31

All probability values lie within the range of +1 to -1.00.

Question 32

Under the normal curve, the probability of any score falling below the 50th percentile, is

A) 0
B) .16
C) -.50
D) .50

Question 33

Under the normal curve, the probability of any single score being between z scores of + 3.00, is

A) 1.00
B) -1.00
C) .99
D) .50

Question 34

Under the normal curve, the probability of any single score falling below the mean is

A) 0
B) .16
C) .34
D) .50

Question 35

The probability of obtaining a z score of +1.00 or lower, is

A) 1.00
B) .16
C) .84
D) .34

Question 36

No probability value may ever be greater than

A) 1.00
B) .99
C) 0
D) there is no upper limit to the size of a given probability value

Question 37

When combining probabilities, to find the probability of one event OR another event, the separate probabilities should be

A) multiplied
B) divided
C) subtracted
D) added

Question 38

When tossing coins, the odds against a "head" turning up are

A) .50
B) .50%
C) 1 to 1
D) 2 to 1

Question 39

The reason z scores may be used to calculate probabilities is that

A) frequencies are easily converted into probabilities
B) all z scores are independent of each other
C) all z scores are included within a standard deviation unit (plus or minus) of the mean
D) all z scores are included within 2 standard deviation units (plus or minus)

Question 40

The probability of obtaining a z score of 0 or above is

A) 0
B) .16
C) .34
D) .50

Question 41

When the odds against an event occurring are 9 to 1, the probability that the event will occur is .10.

Question 42

A negative z score must yield a positive probability value.

Question 43

The "Gambler's Fallacy" overlooks the fact that probability values may never be greater than 100.

Question 44

The probability of any event occurring above the mean is at least .68.

Question 45

When events are included between two negative z scores the probability value for those events must be less than .50.

Question 46

Under the normal curve, the exclusion of the most extreme scores refers only to the highest scores in the distribution.

Question 47

The ratio, specific event divided by total events, defines probability.

Question 48

The mean weight for a group of students is 130 pounds, with an SD of 8 pounds. What is the probability of selecting a single student who weighs 125 pounds or more?

Question 49

Probability is always stated in terms of how often an event will occur.

Question 50

On a normal distribution 68% of the cases must fall above the mean

Question 51

When a specific event has a probability value of .05, then its frequency of occurrence is 95%.

Question 52

When an event must occur, its probability is 100.

Question 53

If a coin is flipped 10 times, and by chance, heads turn up 10 times, on the next flip the probability of again obtaining a head is .50.

Question 54

An event which occurs at a high frequency also has a high probability of occurring.

Question 55

The probability of any event falling within one standard deviation of the mean (plus or minus) is .

Question 56

No probability value can ever be greater than 1.00.

Question 57

The mean is 55 with an SD of 15. What is the probability of selecting at random a score which falls between 60 and 65?

Question 58

A probability value of 0 indicates that the event can never occur

Question 59

The probability that any given event may be included between two positive z scores must be greater than .50.

Question 60

When an event occurs at a frequency of 95%, its probability value is .05.

Question 61

With a mean of 95 and an SD of 12, what is the probability of selecting at random a score of between 89 and 101?

Question 62

A certain air-force missile has an average range of 1500 miles with a standard deviation of 62 miles. What is the probability that any single shot will travel 1400 miles or less?

Question 63

Using data from the previous problem, what is the probability of selecting an inmate who had NOT recidivated?

A) .36
B) .64
C) .50
D) .46.

Question 64

With a mean of 60 and an SD of 4, what is the probability of selecting at random a score between 56 and 58?

Question 65

With a mean of 55 and an SD of 6, what is the probability of selecting at random someone scoring between 48 and 50?

Question 66

At a certain race track, the horses run the mile in an average time of 135 seconds, with an SD of 13 seconds. What is the probability of selecting at random a horse that could run the mile in 130 seconds or less?

Question 67

In a certain house of correction, 64% percent of the current population of inmates had recidivated. What is the probability of selecting an inmate at random who had recidivated?

A) .36
B) .64
C) .50
D) .46

Question 68

At a certain prison it was found that 71% of the inmates had had a first arrest at the age of 15 or younger. It was also found that 70% of the population were identified as having had a drug problem. What is the probability of selecting at random an inmate who had been arrested at 15 or younger and had also been identified as having a drug problem?

A) .14
B) .50 c .95
D) .46

Question 69

With a mean of 70 and an SD of 10, what is the probability of selecting a score of between 75 and 90?

Question 70

The mean IQ in a certain sorority is 120 with an SD of 5. What is the probability of selecting at random a student whose IQ is between 130 and 135?

Question 71

Using data from the previous problem, what is the probability of selecting at random a participant who had had a losing evening?

A) .12
B) .24
C) .48
D) .88

Question 72

At a certain college, the mean college-board score in math is 400 with an SD of 97. What is the probability of selecting at random a student who scored between 370 and 450?

Question 73

If the probability of a certain event is .50 and the probability of a second event is .50, what is the probability of having the first event occur OR the second event occur?

A) .25
B) .50
C) .75
D) 1.00

Question 74

The average life of a certain light bulb is 200 hours with an SD of 27 hours. What is the probability of selecting at random a bulb lasting 150 hours or less?

Question 75

At a certain casino on a certain day, 12% of the participants left at the end of the evening as winners (had more money than when they entered). What is the probability of selecting at random a participant who had had a winning evening? a .12

A) .24
C) .48
D) .88

Question 76

With a mean of 40 and an SD of 20.45, what is the probability of selecting at random a score of 45 or higher?