Flashcards in Chapter 13 : Single Sample t-Test Deck (26):

1

## When do you use the Z-test?(2)

###
-When the mean and standard deviation of the null-hypothesis population are KNOWN.

- Usually you will only have the mean.

2

## When population standard deviation is UNKOWN what test do you use?

### - t-Test

3

## What are the three kinds of t-tests?

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- Single Sample t-Test

- Correlated samples t-Test

- Independent Samples t-Test

4

## What is the t-test formula, what data does it involve??????Difference with z-test?

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- Tobt= Xobt- u/ Sx

**Sx= standard error of sample…

- Z formula uses POPULATION data not sample

5

##
Probability distribution of t-values:

- variation in t values?

- Probability ?

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- different possible t values for samples of a given N

- Probability of getting each value if sampling is random from the null hypothesis population.

6

##
Characteristics of Sampling distribution of T ?

- shaped similarly to z distribution if: (2)

###
-Sample size X >/= 30

-If Ho population is normally distributed

7

## There is a different curve for each ___(_).

### - sample size (N)

8

##
What are Degrees of freedom? (df)

- When is this the most relevant ?

###
- number of scores that are free to vary in calculating any statistic.

- Most relevant when dealing with standard deviation.

9

## What is the formula for the sum of deviations about the mean?

### s = \/E(X-Xbar)^2/N-1

10

## What is the formula for Xbar?

### Xbar= EX/N

11

## T and Z distributions are both ____ at zero. As the df increases, t becomes __ similar to z. As df approaches infinity, t becomes ____ to z. At any value of df ___.

###
- symmetrical

- more

-identical

-more

- Tcrit>Zcrit

12

## Steps to solving single sample t-test problems?

###
1. solve for tobt

2. find the df

3. find tcrit on table D using Df and alpha

4. If | tobt |>| tcrit |, reject Ho

13

## What is the formula for calculating Tobt directly from raw scores? Benefit?

###
- Tobt= Xbar obt - u/ >/SS/N(N-1)

- no need to calculate S

14

## What does the IB has a real effect mean?

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- Tobt is greater than Tcrit

- rejected Ho

15

## What is the magnitude of the real effect?

### - statistical significance vs practical significance.

16

## Measures of effect size are calculated using what?

### - Cohen's d

17

## Cohen's d is?(2)

###
- relationship between mean difference and effect size, Mean diff= Xobt-u

- main interest is magnitude..absolute value!

18

## Choen's d is _____. Divided by the __ standard deviation.

### - standardized, sample

19

## What is the computational equation for effect size for single sample T-tests?

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- d= | xobt- u |/ s

Xobt= sample mean

u= population mean

s= sample standard deviation

d= estimated d

20

##
Often the ___ mean is unknown. We use the __ mean to estimate the ___ mean.

###
- population

- sample

- population

21

## Point estimate??

### - uses only one value to estimate population mean

22

## Interval estimate??

### - uses a range of values to estimate population mean

23

##
What are confidence intervals?

Confidence limits?

###
- range of values which probably contain the population mean.

- values that bound the confidence interval

u lower= Xobt- Sxtcrit (Sx = s/ >/N)

u upper= Xobt + Sxtcrit

- can be CI of 95% or 99%

24

##
-If the confidence interval is 99% what is the range?

-what of 95%?

### - -t 0.025 <= t 0.005

25

## List the steps to solving for a confidence interval!

###
1. find Sx

2. examine alpha, if it's one or two tail,

3. find df

4. Solve for the lower and upper limits

5. conclude with the interval.

26