Stats final

What is inferential statistic?

Drawing conclusions about a population based on data from a sample of that population

Any quantity computed from the values in a sample is called _________

Statistics

The population characteristic is called ________

Parameter

Statistics are also called?

Estimates

What is the problem with using statistics to estimate parameters?

The estimates usually aren’t correct

What does the value of the statistic based on?

The sample selected

What is sampling variablilty?

The varying of the statistic value from sample to sample

What is the distribution of statistic (estimates) called?

Sampling distribution

What is sampling distribution based on?

All possible samples of the sample size

What is the most important features of a sample distribution?

Shape, center and spread

What is the central limit theorem?

When n is sufficiently large, a sample distribution of x bar is well approximated by a normal distribution

When the population distribution is normal, what is true about the sampling distribution?

The sampling distribution is also normal for any size of n

As sample size increases, what happens to variability?

It decreases

How large is sufficiently large?

Greater than 30

As sample size increases, what happens to the standard deviation?

It decreases

As sample size increases, what happens to the probability?

It increases

What is the primary goal of sampling?

To reach conclusions about one or more characteristics of the population from which the sample was selected

What's the only way you can find the true value of the population proportion (p)?

Conducting a census

How do statisticians estimate P?

By taking a sample and computing the sample proportion

When N is large and P is not too close to zero or one what is true about the sampling distribution

It is approximately normal

What happens to the probability if N is increased?

It will decrease

When the sample size increases what happens to the variability

It decreases

What is a point estimate

A single number that represents a plausible value for the population parameter

What is an interval estimate

A range of plausible values for that parameter

Which type of estimate increases the probability of correctness

Interval estimate

What is a trade off for interval estimate

It is not as useful and confident

What are the two things to look for when choosing a statistic to estimate a population parameter

No bias and low variability

What is an unbiased statistic

A statistic with a mean value that is equal to that of the population characteristic being estimated

What is an example of a biased statistic

Sample range to estimate the population rate

When given a choice between several unbiased statistics which one should you use

The one with the lowest standard deviation

Is it better to overestimate or underestimate

Overestimate

What is a confidence interval

An interval of plausible values for the characteristic

What is a confidence level

The success rate of the method used to construct the interval

If you want more confidence what do you have to sacrifice

Accuracy

As confidence interval increases what happens to the interva?

The interval is wider

What is the standard error of a statistic

The estimated standard deviation of the statistic

If no prior information is available, what value for p is used?

0.5

Which factors affect the margin of error

The confidence level and the sample size

What can the margin of error be considered as

The length of the interval

When you increase the confidence level what happens to precision

It is less

If you want more precision what do you do the sample size

You increase it

What does it mean to be 90% confident

90% of the intervals produced with this method will capture the true value

What does it not mean to be 90% confident

There is a 90% chance they will catch that value in one interval

What shape is the T curve

Bell shaped symmetric and centered at zero

Is the T curve more or less spread out than the Z curve

More

As the DF increases what happens to the spread of the corresponding T curve

It decreases

As the number of DF increases what happens to the t curve

The T curves get closer and closer to the Z curve

When a sample size is small and it provides data to you what do you have to do

You must graph it

What kind of graphs can you use to check for normality

Histogram dot plot or boxplopt

What attribute do you look for in a graph to test for normalcy

Symmetry

To an appropriate sample size What do you need to find first

An estimate of the standard deviation

As degrees of freedom increases what is true about where the T distribution approaches

The T distributions approach the normal curve

What is a hypothesis a statement of

A population characteristic

What does the rejection of the null hypothesis imply

The acceptance of the alternate hypothesis

What is a type one error

Rejecting the null when it is true

What is a type 2 error

Failing to reject the null when it is false

What symbol is the probability of a type one error represented with

Alpha

What is the probability of a type 2 error represented with

Beta

How does decreasing one type of error affect the other error

Causes the other to increase

Is it possible for alpha or beta to equal zero

No

What does it mean for an error to be made 5% of the time

Five out of every 100 samples taken we would reject the null hypothesis when it's actually true

What is the only way to simultaneously decrease both type of errors

Increase the sample size

What is a test statistic

The function of sample data on which the conclusion to reject or fail to reject the null being used

What is the P value

The probability of obtaining a test statistic value as least as inconsistent with the null when the null is true

What does the value of z tell us

How many standard deviations the observed value is from the hypothesized value