UW-W ECON 245 EXAM 3

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predictive interval

A ________ tells you an upper and lower bound such that a certain percentage of observed data values lie within the upper and lower bounds.

sampling, underlying, data points, mean

A confidence interval is not likely to contain a majority of the data points because: 1) Our confidence levels are made from the _________distribution and not the _________ distribution. 2) Many _________ are typically farther away from the _________.

dispersion (o)

All of our confidence intervals can be thought of as having the following form: point estimate +/- some quantity. The "some quantity" depends on our sample size, our desired confidence level, and the level of ________.

two-sided confidence interval

Allowing the confidence to contain points both greater than and less than the point estimate

1.645

Appropriate z-score for a 90% confidence level

1.96

Appropriate z-score for a 95% confidence level

2.575

Appropriate z-score for a 99% confidence level

o, mean

Constructing a confidence interval around x bar where you know o is pretty dumb, because it supposes you know ________ but you don't know ________.

predictive interval

For any normally distributed phenomenon, a majority of the data points will be found within the intervals.

more likely

If we lower the confidence level of a hypothesis test, we are _________ to reject the null hypothesis

less likely

If we raise the confidence level of a hypothesis test, we are _________ to reject the null hypothesis.

two-sided

If we want to allow for the possibility that our point estimate may be both greater than or less than the population parameter we should construct a _________ confidence interval.

critical value

In order to carry out a hypothesis test, you need to know a test statistic and compare it to a ________.

s

In the event that we don't know o, we work with its very reasonable proxy ________.

accuracy, precision

Large confidence levels will give you high _________ but low _________

believe, evidence

One of the problems with the conclusion "fail to reject the null hypothesis" is that we may not really ________ the null hypothesis, it's just that we haven't marshalled enough ________ to reject it.

precision, accuracy

Smaller confidence levels will give higher _________ but lower _________.

squashed, tails, variance

Some things to note about the t-distribution: 1) Looks like a slightly "_________" normal distribution 2) More mass in the _________ and less in the peak 3) Has a higher _________ than a normal distribution

H1

Suppose I meet with the parole board to see if I should be paroled. The parole board decides I am reformed and frees me only to discover months later that I was far from reformed. Then ________ = I am reformed.

a type 2, no

Suppose you decide to drive drunk under the presumption that you won't get caught. A cop notices that you are drifting, suspects you are drunk, and decides to investigate. The end result is that you have to go to jail for aggravated driving while intoxicated. Then: you committed ________ error, the cop committed ________ error

o, large, small

The basic varieties of the confidence interval formula arise from two considerations. They are: 1) Do we know _________? 2) Is the sample _________ or _________?

William Gosset

The discovery of the t-distribution is generally credited to:S

standard error

The quantity by which we scale our z-score

student

The t-distribution is also known as the ________ distribution.

hypothesis testing

Trying to see if a particular claim is valid or not

sample size

We use the t-distribution when our ________ is small.

small sample size

When is it appropriate to use the t-distribution?

increase of sample size

Which of the following implies we need not face the precision vs. accuracy trade-off?

all of the above are true

Which of the following is not true of the t-distribution?

precision, accuracy

With a confidence interval, as you increase the confidence level: you decrease ________, but increase ________

point estimate+/-some quantity

confidence interval

degrees of freedom

n-1

type 2 error

occurs when fail to reject a false null hypothesis

type 1 error

occurs when we reject a true null hypothesis

interval estimation

primarily takes the form of calculating an interval that we believe contains a population parameter on the basis of information in a sample

t.050

t value for 90% confidence level

t.025

t value for 95% confidence level

t.005

t value for 99% confidence level

null hypothesis

the claim being mad and what we are seeking to test, usually written as H0

margin of error

the maximum sampling error permitted (E)

standard error

the standard deviation of the sampling distribution, using the sample standard deviation

statistical inference

the use of sample statistics to infer something about population parameters

alternative hypothesis

when the null hypothesis is false, usually written as H1

type 1

whenever we lower the confidence level, we are increasing the risk of _________ error

type 2

whenever we raise the confidence level, we are increasing the risk of a _________ error.

fail to reject the null hypothesis

z- or t-score < critical value

reject the null hypothesis, accept the alternative

z- or t-score > critical value


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