Research Methods

Question 1

Where are typical or expected scores in a distribution found?

Answer 1

relatively close to the mean

Question 2

two measures that are important characteristics of distributions of data…

Answer 2

mean and standard deviation

mean = the average
standard deviation = measures how much a set of scores is dispersed around an average measure of variability.

Question 3

what is standard error?

Answer 3

1. the standard deviation of the distribution of sample means
2. a measure of expected average distance between a sample mean and the population mean

Question 4

what is the distribution of sample mean?

Answer 4

the collection of all possible sample means of a given size (n) from a population

Question 5

What does central Limit theorem tell us?

Answer 5

it tells us that the population mean will be the same as that of the distribution of sample means

• the precise characteristics of a distribution of sample means for samples of any size
• that large sample sizes of over 30 will have a normal distribution

and provides us with the standard error which is the standard deviation of the distribution of sample means

Question 6

what is normal when n > 30

Answer 6

the shape of the distribution of sample means - normal distribution

Question 7

to make inferences about a sample mean where both THE POPULATION MEAN AND STANDARD DEVIATION ARE KNOWN - which test do we use?

Answer 7

z-test

Question 8

When do we REJECT the null hypothesis?

Answer 8

if the sample mean has a low probability (p<0.05)

Question 9

SINGLE SAMPLE T TEST

Answer 9

involves calculating a t-statistic for the sample mean comparing the sample mean with a given number

• • if the t score is found to be extreme for the degrees of freedom the probability is small so we must reject the null hypothesis
• other forms of t-test research designs are repeated measures and independent measures design

Question 10

independent and repeated measures t tests looks for????

Answer 10

significant differences…

Question 11

when do you use a t-test?

Answer 11

if the population standard deviation is unknown

Question 12

repeated measures t tests look for..

Answer 12

a significant difference between mean times 1 and times 2 - before and after

Question 13

independent measures t test looks for

Answer 13

a significant difference between the two groups - control and experiment – and the null is H0:U1 = u2

Question 14

how do we describe distributions?

Answer 14

central tendency = mean

variation = standard deviation

Question 15

as sample sizes increase…

Answer 15

standard error decreases

Question 16

pearson correlation co-efficients

Answer 16

r = sample correlations
size of r shows the strength of the correlation and how close to the line it is and sign (+ or - ) shows the direction
rho = is the population correlation

the value of r lies between -1 and +1
and an r = 0 means no association at all

Question 17

what do correlations look for

Answer 17

a relationship between two variables

• in a positive correlation both variables increase
• in a negative correlation as one variable increases the other decreases

Question 18

the larger the degrees of freedom…

Answer 18

the lower the critical limit

Question 19

the z test cannot be used when:

Answer 19

the population standard deviation is not known

when you want to compare the means of 2 different samples

and when you want to compare change in a sample over time

Question 20

what does a single sample t test do?

Answer 20

compares the sample mean with a given number