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77 Cards in this Set
 Front
 Back
Which of these are typically used more? Population or Sample

Sample: gathering data from an entire population is usually impractical


What is assumed when collecting data for a sample

That the sample is drawn from a population of INFINITE size


What is the best way to achieve a representative sample

By selecting the sample at random


What are the different ways to do a random sampling

1)Systematic sampling
2)stratified sampling 

Why is it nearly impossible to do a random sampling

Because the people still need to volunteer


Definintion
Sampling Error 
The amount of error in estimating a population parameter (mean, SD, etc...) from a sample
The mean of the sample might not be exactly equal to the population, so the difference is taken (Sampling error) 

Abbriviation
SEM 
Standard Error of the Mean


Formula
SEM = ? 
SEM = s/sq. rt. n
s = sample standard dev. n = sample size It is the estimate of how much the sample mean differs from the population mean 

When Sample Size increases, what happens to the Sampling Error

it decreases
the decrease is less noticable the larger the sample size gets 

Definition
Research Hypothesis 
A prediction outcome based on theoretical consideration. An informed guess
Also known as a Scientific Hypothesis 

Definition
Null Hypothesis 
A statement about the numerical value of a unknown parameter
Also known as a Statisical Hypothesis The hypothesis of no difference between two groups 

More info
Null Hypothesis 
the hypothesis is often the reverse of what the experimenter actually believes
Put forward to allow the data to contradict it 

What is the purpose of the null hypothesis

It is important to be able to state with confidence that the effect was really due to chance
Hypothesis tests starts with the assumption that the effect was due to chance, that there was no difference between means of the treatment group and control 

What will the number of hypotheses depend on?

The number of IV and DV


With more than one IV?

more than one hypothesis


With more than one DV?

Sometimes combined and sometimes stated separately
Depends on the nature of the relationship between the DV's 

What are some neccessities of a hypothesis in an experiment

elements being compared should be stated
the hypothesis should clearly describe the relationship hypothesis should be as concise as possible should understand the relationship to be tested 

What are some components of a good hypothesis

Concise
Operational hunches can be emperically assessed May be restated in null form Stated in declarative form Posit a relationship between variables Reflect a theory/body of literature Testable 

What are some components of a bad hypothesis

long
contradictory illogical uninterpretable refer to "differences in the DV" relationship and difference used in the same sentence 

What are the characteristics of the Normal Curve

Unimodal
Symmetrical Mean, Median, Mode all the same score Areas under the curve described by standard deviation Tails approach, but never touch, horizontal axis (Asymptotic) 

What is the most common standard score used with a normal distribution

The Zscore


Definition:
Z Score 
The standardized score used to produce a normal curve with mean=0, and s=1


What does the Z score represent

A raw score expressed in standard deviation units


Formula:
z = ? 
z =(XMean)/s


What needs to be known for the raw score to be represented as a zscore

the mean and standard deviation


What can a zscore be used to describe for a normal distribution

the percentage of the normal curve contained within 2 zscores or a zscore and the mean


+ or  1 sd=
+ or  2 sd= + or  3 sd= 
68%
95% 99% 

What is an example of a standard score

a T score


Formula:
Skewness (SK)= 
{n/[(n1)(n2)]}xsum of z^3


Definition
Probability 
the porportion of the time you were successful
Also known as the p value statisical viewpoint: the likelihood that your results are due to chance 

What is the range of probability

0 to 1
0=no way you'll be successful 1=you will win every time You can't have a negative probability 

What is the probablility of an even?

the number of favorable outcome divided by the total number of poddible outcomes


What is a frequency distribution

the total # of scores


Definition:
Probability 
the number of times an event occurs of the total possible number of sample points


Definition:
Sample Space 
The total possible sample points


How does probability change

based on how you state what you want your successes to be


What formulas are used for determining sample spaces for statistical testing

Permutation Formulas
Combination Formulas 

What is used to compute the probability of a particular score to occure

the z score and the corresponding area of the normal curve


Definition
Conditional Probability 
The probability of an event given that another event has occured


Definition
Permutation 
an arrangement of a set of objects in which their order is considered


Formula
Permutation 
nPr = n!/(nr)!


Definition
Combinations 
A distinct set of objects in which the order is not considered


Formula
Combinations 
nCr = n!/r!(nr)!


What are Confidence Intervals

An actual estimate of the population mean and are based on a probability distribution


95%CI = ?

95%CI = Mean +or 1.96(SEM)
SEM = s/sq.rt. n 

When is it a Type I/Type II error

Decision Accept Reject
Ho True: Correct TypeI Ho False: TypeII Correct 

Type I error

True Ho Rejected
A researcher reports a difference when there is none 

What is the probability called when making a Type I error

alpha level or level of significance
"the probability of observing that outcome is less than 5%" 

What is the probability calles when making a Type II error

Beta and is set by Power


Formula
Power = ? 
Power = 1  beta
typically set as 0.8 meaning that the researcher is willing to take a 20% chance of making a Type II error 

How can a researcher control Power

1)Increase the difference between Means
2)Decrease the Variance 3)Increase the Sample Size (easiet to control) 

What will calculating the power allow us to do

To determine the number of subjects needed to have adequate POWER so as to avoid the Type II error


When is the power calculated

Once the research is complete and be based on the data from the research


What is the 7 step procedure for testing hypotheses with the one sampled z test

1)State the null hypothesis
2)Do a one sample z test 3)state the level of significance for test 4)Write the tabled critical region value 5)Calculate 6)Compare calc. z score to critical z and make decision 7)state your conclusion 

What does the one sample t test tell us

if the smaple mean is significantly different than the population mean


Why is the t distribution used (also called the Student's t distribution)

it is rarely the case that all the sample data has a perfectly normal distribution


What is the 7 step procedure of the one sampled t test

the same as the z test but using the one sample t formula in the calculations


What is assumed in the onesampled ttest

Randomness
Normally distributed Interval/ratio type mu is known 

When is the Independent ttest (or the twosample ttest) used

when comparing 2 sample means rather than a sample mean to a population mean


What is assumed in the onesample ztest

Randomness
Normally Distributed scores Interval/ratio type mu and sigma are know 

what is assumed with an independent ttest

Randomness
Normality Interval/ratio data 2 independent group 10 or more participants per group Equal variance 

When do you have to worry about equal variances

If the group sizes are not equal, then a test for the assumption of equal variances must be tested


What is the test for equal variance called

Levene's test
if equal, avg. the variances for the groups if unequal, the t calculated using seperate variances not avg. 

What is the 7 step procedure for testing the hypothesis

same as before only using the twosample ttest when calculating


Formula
CI for mean difference 
95%CI= mean1  mean2 +or (tabled critical t)(SED)
SED = sq.rt. [(s1^2/n1)+(s2^2/n2)] 

Based on the CI, when would we reject/accept the null

reject the CI DOES NOT contain 0 in the range
accept the CI DOES contain the 0 in the range 

What is Effect size used for

used before the study to estimate the sample size


Effect Size

calculated to see the magnitude of the difference between 2 means after the study
helps to estimate the meaningfulness of the treatment used to describe the difference between the mean of the Exp. and the Cont. Simply a z score (Mean_e  Mean_c)/s_c 

in what units is the effect size expressed in

standard deviation units


What are the two ways of evaluating the effectiveness of a treatment

1)Effect Size
2)Omega Squared 

When should the Omega squared be calculated

After a ttest if a significant difference is found


Why is the Omega Squared calculated

Gives researchers and indication of how effective the treatment variable is
Indicates the proportion of the variance in the dependent variable that is explained by the independent variable 

What does the independent ttest assume about the groups

that they are not related to each other in any way


What is it meant by using related samples

there is a single group of subjects with a dependant variable being measured on more than one occassion under more than one condition


When do we use a paired ttest
(also known as the Dependent ttest) 
when the results of two different measurements depends on each other
pairs of participants are matched on one or more characteristics and randomly placed into 2 groups Twin studies 

What are the 7 steps procedure for testing the hypothesis

same as all the others but using a different formula


What is assumed in the dependent ttest

Randomness
normality interval/ratio two dependent samples of measures 