# Developing Study Skills and Research Methods Unit Leader: Dr James Betts Unit Code: HL20107

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Developing Study Skills and Research Methods Unit Leader: Dr James Betts Unit Code: HL20107 J.Betts@bath.ac.uk

Refresher Test Level of Measurement? Discrete/Continuous? –Academic Grade (A*-F) –Tides (+/-1 m, etc.) –Nationality –Body Mass (kg) –Social Class –Date (DD/MM/YYYY) –Colour (nm) –Shoe Size

Indicators of Central Tendency Mode (i.e. most frequently occurring score) + – Median (i.e. middle score/50 th percentile) + – Mean (i.e. arithmetic average) + –

Normal Distribution

LogicalStatistical AKA Criterion FaceContentPredictiveConstructConcurrent Validity ConsistencyReliabilityObjectivity

Logical Validity Face Validity –Infers that a test is valid by definition –It is clear that the test measures what it is supposed to Content Validity –Infers that the test measures all aspects contributing to the variable of interest

Statistical Validity Concurrent Validity –Infers that the test produces similar results to a previously validated test Predictive Validity –Infers that the test provides a valid reflection of future performance using a similar test

Logical/Statistical Validity Construct Validity –Infers not only that the test is measuring what it is supposed to, but also that it is capable of detecting what should exist, theoretically –Therefore relates to hypothetical or intangible constructs

Threats to Internal Validity Maturation History Pre-testing Statistical Regression Instrumentation Selection Bias Experimental Mortality.

Threats to External Validity Inadequate Description Biased Sampling Hawthorne Effect Demand Characteristics Operationalisation.

Reliability Subject 1 60 ml.kg -1.min -1 60 ml.kg -1.min -1 60 ml.kg -1.min -1 Subject 2 55 ml.kg -1.min -1 55 ml.kg -1.min -1 55 ml.kg -1.min -1 Subject 3 70 ml.kg -1.min -1 70 ml.kg -1.min -1 70 ml.kg -1.min -1

Reliability Subject 1 60 ml.kg -1.min -1 65 ml.kg -1.min -1 65 ml.kg -1.min -1 Subject 2 55 ml.kg -1.min -1 60 ml.kg -1.min -1 60 ml.kg -1.min -1 Subject 3 70 ml.kg -1.min -1 75 ml.kg -1.min -1 75 ml.kg -1.min -1

Reliability Subject 1 60 ml.kg -1.min -1 72 ml.kg -1.min -1 57 ml.kg -1.min -1 Subject 2 55 ml.kg -1.min -1 61 ml.kg -1.min -1 52 ml.kg -1.min -1 Subject 3 70 ml.kg -1.min -1 40 ml.kg -1.min -1 84 ml.kg -1.min -1

Relative Reliability Subject 1 60 ml.kg -1.min -1 63 ml.kg -1.min -1 57 ml.kg -1.min -1 Subject 2 55 ml.kg -1.min -1 56 ml.kg -1.min -1 48 ml.kg -1.min -1 Subject 3 70 ml.kg -1.min -1 65 ml.kg -1.min -1 66 ml.kg -1.min -1

Rater Reliability Intrarater reliability –The consistency of a given observer or measurement tool on more than one occasion Interrater reliability –The consistency of a given measurement from more than one observer or measurement tool

Example Hypotheses: Isometric Torque Is there any difference in the length of time that males and females can sustain an isometric muscular contraction? Null Hypothesis (H 0 ) There is not a significant difference in the DV between males and females Alternative Hypothesis (H A ) or experimental (H E ) There is a significant difference in the DV between males and females.

Example Hypotheses: Isometric Torque Is there any difference in the length of time that males and females can sustain an isometric muscular contraction? Null Hypothesis (H 0 ) There is not a significantly higher DV for males than for females. Alternative Hypothesis (H A ) or experimental (H E ) There is a significantly higher DV for males than for females.

Example Hypotheses: Isometric Torque Is there any difference in the length of time that males and females can sustain an isometric muscular contraction? 16 17 18 19 20 Sustained Isometric Torque (seconds) N N n n

Statistical Errors Type 1 Errors Type 2 Errors

SPSS Outputs

Example Hypotheses: Isometric Torque Is there any difference in the length of time that males and females can sustain an isometric muscular contraction? 16 17 18 19 20 Sustained Isometric Torque (seconds) t-test Mean A Mean B

Example Hypotheses: Isometric Torque Is there any difference in the length of time that males and females can sustain an isometric muscular contraction? 16 17 18 19 20 Sustained Isometric Torque (seconds) Mean A Mean B

SPSS Outputs

So which stats test should you use? Q1. What is the LOM? Q2. Is the data ND? Q3. Is the data paired or independent?