Alternative hypotheses.
Experimental and null hypotheses.
Directional (one-tailed) and non-directional (two-tailed) hypotheses.
Observations of events or behaviour in our surroundings provoke questions as to why they occur. In turn, one or multiple theories might attempt to explain a phenomenon, and investigations are consequently conducted to test them. One observation could be that athletes tend to perform better when they have a training partner, and a theory might propose that this is because athletes are more motivated with peers around them.
The aim of an investigation, driven by a theory to explain a given observation, states the intent of the study in general terms. Continuing the above example, the consequent aim might be “to investigate the effect of having a training partner on athletes’ motivation levels”.
The theory attempting to explain an observation will help to inform hypotheses - predictions of an investigation’s outcome that make specific reference to the independent variables (IVs) manipulated and dependent variables (DVs) measured by the researchers.
There are two types of hypothesis:
H1 – Research hypothesis
H0 – Null hypothesis
This predicts a statistically significant effect of an IV on a DV (i.e. an experiment), or a significant relationship between variables (i.e. a correlation study), e.g.
In an experiment: “Athletes who have a training partner are likely to score higher on a questionnaire measuring motivation levels than athletes who train alone.”
In a correlation study: ‘There will be a significant positive correlation between athletes’ motivation questionnaire scores and the number of partners athletes train with.”
The research hypothesis will be directional(one-tailed) if theory or existing evidence argues a particular ‘direction’ of the predicted results, as demonstrated in the two hypothesis examples above.
Non-directional (two-tailed) research hypotheses do not predict a direction, so here would simply predict “a significant difference” between questionnaire scores in athletes who train alone and with a training partner (in an experiment), or “a significant relationship” between questionnaire scores and number of training partners (in a correlation study).
This predicts that a statistically significant effect or relationship will not be found, e.g.
In an experiment: “There will be no significant difference in motivation questionnaire scores between athletes who train with and without a training partner.”
In a correlation study: “There will be no significant relationship between motivation questionnaire scores and the number of partners athletes train with.”
When the investigation concludes, analysis of results will suggest that either the research hypothesis or null hypothesis can be retained, with the other rejected. Ultimately this will either provide evidence to support or refute the theory driving a hypothesis, and may lead to further research in the field.
State the independent variable (IV) of the investigation carried out by Tobias. (1) October 2019 P2
Identify the independent variable (IV) from the experiment conducted by Cherry. (1) January 2020 P2
State the independent variable (IV) of Harbinder’s experiment. (1) June 2017 P2
State the dependent variable (DV) of Harbinder’s experiment. (1) June 2017 P2
Identify the independent variable in this study. (1) June 2016
Identify the dependent variable in this study. (1) June 2016
State how the dependent variable (DV) has been operationalised in Zulikhat's study. (1) June 2019
Identify the fully operationalised independent variable (IV) for this experiment. (1) January 2020
Give two operationalised variables Tau may have used in his investigation. (2) October 2018 P2
Give a fully operationalised non-directional (two-tailed) hypothesis for this study. (2) October 2016
State a non-directional (two-tailed) hypothesis for this study. (2) June 2017
State the independent variable (IV) and dependent variable (DV) for this study. (2) January 2018
State a non-directional (two-tailed) null hypothesis for this investigation. (2) June 2018
State a directional (one-tailed) alternative hypothesis for the high school study. (2) June 2019
State a fully operationalised directional (one-tailed) hypothesis for the experiment Oti carried out. (3) June 2018 P2
State a one-tailed (directional) hypothesis for this study. (3) June 2016 P2