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Reliability and Validity Reliability and Validity

Reliability and Validity - PowerPoint Presentation

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Reliability and Validity - PPT Presentation

Thinking Questions What is an IV What is a DV What is repeated measures design What is matched pairs design What is independent groups design What is a hypothesis Can you name the 3 types ID: 294084

results validity words reliability validity results reliability words time hypothesis test design memory marks participants study reliable researcher directional page mark measure

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Presentation Transcript

Slide1

Reliability and ValiditySlide2

Thinking Questions

What is an IV?

What is a DV?

What is repeated measures design?What is matched pairs design?What is independent groups design?What is a hypothesis? Can you name the 3 types of hypothesis?Slide3

Learning Objectives:

1) To develop an understanding of reliability and validity in psychological studies.

Success Criteria:

1) Complete page 21 of your booklet making notes on types of reliability.

2) Answer practice questions on page 22 of your booklet on validity.Slide4

But first…Slide5

Past Exam Question

A researcher carried out an experiment to investigate how many numbers could be held in short-term memory. The participants were 15 children and 15 adults. Participants were asked to repeat lists of random numbers, in the correct order, as soon as they were read out by the researcher. For example, when the researcher said, “3, 4, 2, 8” the participant immediately repeated “3, 4, 2, 8”. When the researcher then said,“7, 5, 9, 6, 4” the participant immediately repeated “7, 5, 9, 6, 4”. One number was added to the list each time until participants were unable to recall the list correctly. Each participant’s maximum digit span was recorded.

(a) Write an appropriate non-directional hypothesis for this experiment.

AO3 = 2 marks

0 marks for a directional hypothesis.

1 mark if not

operationalised

, e.g. “Age affects memory.” “There will be a difference between the two conditions.”

2 marks for e.g. “There will be a difference in how many numbers are correctly recalled by children and adults.”

“Children and adults have different short-term memory spans.”

Or

“The capacity of short-term memory is different for adults and children.Slide6

Past Exam Question

A researcher investigated whether memory for words presented with pictures was better than memory for words presented without pictures. The researcher used an independent groups design.

In

Condition 1, participants were given a limited time to learn a list of 20 words. They were then asked to recall the 20 words in any order.

In

Condition 2

, participants were given the same time to learn the same 20 words, but this time each word was presented with a picture. For example, the word ‘apple’ was presented alongside a picture of an apple. They were then asked to recall the 20 words in any order.

State a non-directional hypothesis for this experiment. (2)

Explain

two

reasons why it was more appropriate to use an independent groups design than a repeated measures design. (4)

1. AO3 = 2 marks

0 marks

for a directional /

correlational

/ null hypothesis.

1 mark

for an appropriate non directional hypothesis where either or both variables are not

operationalised

e.g. memory will be different in the two conditions and / or when the hypothesis is not written as a statement e.g. “ To see if ...” or “ Is there.....?”

2 marks

for an appropriate non directional hypothesis where both variables are

operationalised

e.g. there will be a difference in the number of words correctly recalled when words are presented with pictures and without pictures.

2.

AO3 = 4 marks

Reasons for using an independent groups design rather than repeated measures include:-

There are no order effects because participants only do the task once.

The same words can be used in both conditions so one set of words is no easier to recall than the other set of words.

Demand characteristics are less likely because participants will be unaware of the other condition.

Credit other appropriate reasons.

Simply stating IGD is quicker / saves time = 0.

In each case

1 mark

for a very brief / slightly muddled potentially relevant reason that could explain the use of IGD.

2nd mark

for some elaboration of a reason that is relevant / appropriate to this study.Slide7

Reliability

We could just measure something using a piece of string, but it wouldn’t be very accurate

We need to be able to measure or observe something time after time and produce the same or similar resultsSlide8

Reliability

The best way to test the reliability of an experiment is to

repeat

it. If the same results are obtained, then the experiment is reliable.

Scientists need their results to be

reliable

in order for them to be considered

valid

. Results are

reliable

if they are

consistent

; this means

a test gives the same results each time.

A questionnaire’s reliability can be tested using the

test-retest

method – if the same answers are given the second time, it is a reliable test. Open questions and unstructured interviews lack reliability because they are difficult to replicate.

Why

do the darts in the picture represent reliability?Slide9

Reliability

The equation for checking reliability is:

Total agreements

>80% Total observationsSlide10

Page 21

Booklet – answer the questions at the bottom of...

Using the textbook (page 106)Slide11

Practice Question

Mary has failed her maths GCSE last year. She got the lowest mark in the school, despite being given a Maths award before the exam results were announced. The school were really confused about Mary’s score and allowed her to retake the exam. On her second attempt Mary scored 100%.

Do you think that the Maths GCSE paper was a

reliable measure of Mary’s Maths ability? Discuss your answer with your neighbour.Slide12

ValiditySlide13

Page 22

BookletSlide14

Internal Validity

The extent to which study is free of design faults, which may affect results.

Internal validity also looks at whether the IV really caused the changes to the DV or whether the results were due to

extraneous variables. To have high internal validity you must make sure that you are testing what you intended to test.Slide15

External Validity

This means the extent to which generalisation can be made from the test environment to other situations. If the study lacks internal validity that external validity will also be low and you cannot generalise the results.

Types of external validity include:

Ecological validity – generalising results to other placesPopulation validity

– generalising results to other people

Historical validity

– generalising results to different timesSlide16
Slide17

Generalisability

All psychologists want to be able to generalise their results beyond the research setting and into real life.

A study could even be in the natural environment, but you may not be able to generalise, for example if the study was conducted using American students...why?

So, remember, even when the study is in the natural setting you can not always generalise!Slide18

Does a driving test measure your competence to drive on the road or is it a measure of your ability to pass the driving test? Would you be able to pass it again in six months time? Would you do better? Is it a reliable and valid test?

LSlide19

Task

Complete the table at the bottom of page 22Slide20
Slide21

Look at this image...Slide22

Homework

Create flashcards reliability and validity.