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- Statistics 260
- Mc Cracken
- Final Practice Exam ST 260

Jonathan B.

A professor of math refutes the claim that the average student spends 3 hours studying for the midterm exam. Which hypothesis is used to test the claim?

H0: µ = 3, H1: µ ≠3

The simple linear regression model assumes that regardless of the value for x, the standard deviation of the distribution of y values about the regression line is the same.

true

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a .95 confidence coefficient is equivalent to a 5% significance level

true

Continuous Probability distributions describe probabilities associated with random variables that take on any value along a given range with no gaps between possible values

true

Daily ambient temperatures in degrees Fahrenheit are being recorded for a global warming study. This scale of measurement for this data would be:

Interval

The average labor time to sew a pair of denim jeans is 4.2 hours with a standard deviation of 30 minutes. If the distribution is normal, then the probability of a worker finishing a pair of jeans in less than 3.5 hours is:

.0808

A typical example of dependent samples occurs when we have before-and-after measures of the same individuals.

true

Directional assertions lead to what is called a two-tail test

false

The number of hungry people in Ethiopia is an example of a discrete random variable

True

Reducing the probability of a Type I error reduces the probability of a type II error

False

Failure to reject a null hypothesis means that it is true

false

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The __________ is a graphical display providing cumulative values for frequencies, relative frequencies, or percentages.

ogive

If n = 64, x bar = 53.5, and σ = 10, then the value of the test statistic is:

z=2.80

n publishing the results of some research work, the following values of the coefficient of determination were listed. Which one would appear to be incorrect?

Any one that is negative, because the CoD is a squared result

TermA political analyst in Texas surveys a random sample of registered Democrats and compares the results with those obtained from a random sample of registered Republicans. This would be an example of:

Independent Samples

If a hypothesis is rejected at the .025 level of significance, it:

May or mat not be rejected at .01 level

The MBI Company found that at the end of each month, 2% of its two million accounting entries contained errors. Today, one operator has made 50 computer entries.

What is the probability that at most two errors were made?

What is the probability that at most two errors were made?

.9216

Theoretically, the number of times an event can occur over the given time span in a Poisson distribution has no limit.

true

An important factor in choosing between the pooled-variances t-test and the unequal-variances t-test is whether we can assume the population means might be equal.

False

The power of a test is the probability of making:

A correct decision when the null hypothesis is false

Using the least-squares regression line ŷ = 27,308 + 3747x where salary is the dependent variable and years of experience is the independent variable, predict the salary of an employee with 11 years of experience.

68,525

If the probability of an event is x, with , then the odds in favor of the event are x to (1 - x).

true

The range is a measure of dispersion that includes all the values in the data set in the calculation.

False

If the p-value for a particular hypothesis test is 0.03 with α = 0.05, we do not reject the null hypothesis.

if a>p-value, then we reject the null

Another name for the residual term in a regression equation is:

Random error

The probability of Type I error is referred to as the significance level of the test.

True

In conducting a hypothesis test, we can choose any significance level we desire. In practice, however, levels of 0.10, 0.05, and 0.01 tend to be most common.

True

When a distribution has more values to the right and tails to the left, we say it is skewed positively.

False

The average speed of cars passing a checkpoint is 60 miles per hour with a standard deviation of 8 miles per hour. Fifty (50) passing cars are clocked at random from this checkpoint. The probability that the sample mean will be between 57 and 62 miles per hour is:

.9576

For the values of the coefficient of determination listed below, which one implies the greatest value of SSR (regression sum of squares) given that SST = 500?

0.95

This is because r^2= SSR/SST

The standard error is:

The standard deviation of the sampling distribution

A sample of size 100 selected from one population has 60 successes, and a sample of size 150 selected from a second population has 95 successes. The 95% confidence interval for testing the equality of the population proportions equal to:

(-0.156, .090)

A Type I error is the probability of failing to reject a false null hypothesis.

False

A Type II error is defined as:

Failing to reject a false null hypothesis

If a test is carried out at a specified significance level (e.g., α = .05), using a larger sample size will reduce the value of β, the probability of making a Type II error.

True

Stating that Wal-Mart’s sales increased 6.2% this quarter when compared to last quarter is an example of descriptive statistics.

True; it isn't stating that something should be done. It is just giving you information

The z-test is the appropriate test statistic for any population distribution with a small sample size and an unknown population standard deviation.

False

Rejecting a true null hypothesis is called a

type 1 error

Failing to reject a false null hypothesis is a

Type II error

The only sure way to avoid acception false claims is to

never accept any claims

In a one-tailed test there will be two critical values

false

If H1 is P>0.20 what is the null hypothesis?

H0 is P<=.20

What makes up a discrete random variable?

Take on integer values, usually the result of counting. Something like flipping a coin, the number of heads or tails can be and integer up to infinity.

What makes up a continuous random variable?

Take on any value within a range of values with decimals, such as the average of times a coin is flipped that it is heads.

What are the characteristics of a hypergeometric distribution?

It is similar to a binomial distribution, but the probability changes each time. The probability of taking two marbles from 5 red and 5 green without replacement changes the probability with each trial.

What are the characteristics of a Poisson distribution?

Outcome is a success or failure

Average number of successes(the mean) that occurs in a specific region is known

Probability of success is proportional to the size of the region

Probability of success in a extremely small region is virtually zero

Example of a Poisson Distribution

The average number of homes sold by the Acme Realty company is 2 homes per day. What is the probability that exactly 3 homes will be sold tomorrow?

In a normal distribution, the mean, median, and mode are all in the same position on the horizontal axis

true

The total area underneath a normal distribution is equal to

1.0

the binomial distribution goes with a _____ process

Bernoulli

The normal approximation to the binomial involves a

correction for continuity

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