Data analysis and reporting on investigations Flashcards
What is an alternative (experimental) hypothesis?
A statement that the IV will have an effect on the DV
What is a Null hypothesis?
A statement that the IV will not have an effect on the DV (no difference)
What choices does a psychologist have when they have obtained the results from their study?
To accept the experimental hypothesis and reject the null hypothesis or to reject the experimental hypothesis and accept the null hypothesis.
Explain how we decide which hypothesis to pick
the decision about what to do with the hypotheses will be determined by the significance level the results achieve.
The significance level of a test is the maximum probability of accidentally rejecting a true null hypothesis (a decision known as a type one error). The significance of a result is also called its p-value. The maximum level of significance that psychologists generally regard as acceptable is 5% or p
what is a type one error?
Rejecting the null hypothesis when it is in fact true (optimistic) - this is more undesirable than a type 2 because of the implication of the results obtained.
what is a type two error?
Accepting the null hypothesis when in fact it is false (pessimistic).
What is meant by a significance level of P
This means that there is a 5% chance or less chance that the results were due to a factor other than the IV.
- this is the maximum level of chance that psychologists will accept
There is a 5% or less chance of making a type 1 error.
Alternatively it also means that there is a 95% chance that the results were not due to something other than the IV.
If this level of significance is obtained then the null hypothesis can be rejected and the experimental hypothesis can be accepted.
What is meant by a significance level of P
This means that there is a 1% chance or less chance that the results were due to a factor other than the IV.
There is a 1% or less chance of making a type 1 error.
Alternatively it also means that there is a 99% chance that the results were not due to something other than the IV.
If this level of significance is obtained then the null hypothesis can be rejected and the experimental hypothesis can be accepted.
What is meant by a significance level of P
This means that there is a 0.1% chance or less chance that the results were due to a factor other than the IV.
There is a 0.1% or less chance of making a type 1 error.
Alternatively it also means that there is a 99.9% chance that the results were not due to something other than the IV.
If this level of significance is obtained then the null hypothesis can be rejected and the experimental hypothesis can be accepted.
What is meant by a significance level of P
This means that there is a 10% chance or less chance that the results were due to a factor other than the IV.
- A value higher than 5% would be considered not significant.
There is a 10% or less chance of making a type 1 error.
Alternatively it also means that there is a 90% chance that the results were not due to something other than the IV.
If this level of significance is obtained then the experimental hypothesis can be rejected and the null hypothesis can be accepted.
What is an experiment?
An experiment manipulates an independent variable, measures a dependent variable while keeping all other variables constant.
It looks for differences.
This enables cause and effect to be established.
A change in one variable causes a change in the other.
What is a correlation?
This looks at the relationship between 2 variables.
It gathers pairs of scores - one for V1 and one for V2.
A causal relationship cannot be established.
what are descriptive statistics?
Measures of central tendency are averages; they tell you what are typical values for a set of scores - mean, median and mode.
Measures of dispersion - look at the spread or variability in data.- range and standard deviation.
What are inferential statistics?
Psychologists use inferential statistics to make statements of probability about the likelihood of obtaining a particular set of results by chance factors alone. From these statements, reasoned conclusions can be reached about whether a null hypothesis should be accepted or rejected and therefore whether an alternative hypothesis can be accepted or should be rejected.
define the four different levels of data
Nominal - the data are in separate categories e.g. grouping your class in to people who are tall medium or short. Ordinal- the data are ordered in some way e.g. lining your classmates up in order of height. Interval & Ratio - the data are measured using units of equal measurement e.g. measuring you classmates' heights.
