Stats Exam 3

Question 1

Where does a density curve lie on a graph

Answer 1

the x axis

Question 2

What is the total area under a curve?

Answer 2

1

Question 3

What is a continuous probability distribution?

Answer 3

a density curve

Question 4

How do you find the probability association with a normal distribution

Answer 4

• z = x - µ / σ
• then use the Table II

Question 5

What is a percentile?

Answer 5

Solve for X “unstandardize”

x= µ + zσ

Question 6

Define statistic

Answer 6

the value of a statistic will vary from one random sample to the next

Question 7

If the x variable follow a normal distribution with µ and σ, then which rule applies?

Answer 7

68 - 95 - 99.7 %

Question 8

Parameter

Answer 8

the value of a parameter remains constant

Question 9

Define Sampling Error

Answer 9

• Because statistics are random variables
• a slight error associated with the estimate
• x - u

Question 10

What is a sampling distribution

Answer 10

• a probability distribution for all possible samples

Question 11

If the sample is from a normal poulation then what does x bar have?

Answer 11

a normal sampling distribution

Question 12

What is σx?

Answer 12

= σ / square rt of n

Question 13

How are probabilities found?

Answer 13

standardizing using the standard normal table

Question 14

How are percentiles found?

Answer 14

by unstandardizing from the standard normal table

Question 15

Define the Central Limit Theorem

Answer 15

• when the sample size n is large is a normal distribution

Question 16

Define a point estimate?

Answer 16

• single number estimate
• give no indication of the size of the sampling error

Question 17

Will the point estimate equal the true value?

Answer 17

No, because of sampling error

Question 18

What does the margine of error indicate

Answer 18

how big the sampling error might be

Question 19

What is a confidence interval?

Answer 19

a range of estimate for the true population parameter.

= Point Estimate +/- Margin of Error

Question 20

What does level of confidence mean?

Answer 20

how certain we can be that the true value is contained in the interval (%)

Question 21

What also increases as the level of confidence increases?

Answer 21

the width of the confidence interval

Question 22

What happens to the width of the confidence interval when n increases?

Answer 22

the width decreases

Question 23

If you are given the endpoints of a confidenct interval, how do you calculate the mean?

Answer 23

add and divide by 2

Question 24

What weight sparates the value of the heaviest 10% al all books from the 90% (90th percentile) what type of question is this?

Answer 24

unstandardizing- look for Z in table II

Question 25

If you are given *n * in a problem with mean and standard deviation, what is the first thing you need to do?

Answer 25

1. convert σ to σx
2. use z equation
3. look up in table II

Question 26

which equation do you use to obtain the confidence interval?

Answer 26

t-interval ch 8