Chapter 6  PROBABILITY AND HYPOTHESIS TESTING Understanding Statistics for International Social Work and Other Behavioral Sciences Serge Lee, Maria C Silveira Nunes Dinis, Lois Lowe and Kelly Anders (2015). Oxford University Press

HYPOTHESIS TESTING Hypothesis is a statement of an educational hunch or speculation about a presumed relationship in the real world Two types of theses: Research Hypothesis. Such hypothesis predicts how changes in one variable (independent) are proposed to cause or explain changes in another variable (dependent). For example, the average healthcare needs for people without health insurance are twice as much as those who have health insurance. Null Hypothesis. Such hypothesis states that despite what the sample data suggests, after taking into account sampling errors or chance fluctuations, no real relationship or difference exits between the hypothesized statements. For example, children whose parents are supportive of them at school have the same level of self-esteem scores as children whose parents are not supportive.

DIRECTION OF THE HYPOTHESIS When testing a hypothesis, one may use a directional or non-directional hypothesis Directional (one-tailed) hypothesis is used to test hypotheses that researchers are certain of or able to predict the direction that the relationship will fall on the normal curve Non-directional (two-tailed) hypothesis is used to test hypotheses where researchers believe that significant difference do exist but are unsure or unable to predict the direction of the relationship.

Probability of an event = x 100% CONSTRUCTING THE CONFIDENCE INTERVAL Chance is refers to as sampling error that can affect variation between or among variables in sample statistics Probability is a mathematical equation that shows the proportion or fraction of times that a particular outcome will occur Probability of an event = x 100% Confidence interval, allows the researchers to construct an interval or range of scores around a point estimate, and allows the researchers to state a level of confidence in how likely it is that the interval contains the population parameters being estimated

FOUR POSSIBLE OUTCOMES ASSOCIATED WITH HYPOTHESIS TESTING Determine whether to accept or reject the null hypothesis Decision regarding the null hypothesis () The truth regarding the research hypothesis ( Reject Fail to reject is True Correct decision Type II error is False Type I error Lee. Dinis, Lowe, Anders (2015). Understanding statistics for international social work and other behavioral sciences. Oxford University Press

ALTERNATIVE EXPLANATIONS Use the following possible explanations to support findings when the research hypothesis cannot be explained Rival hypothesis. Other variables that may cause a relationship to occur Design flaws. Design flaws occur when the researchers are not careful with the measuring instruments and sampling bias Sampling error. Sampling error usually occurs due to unequal sample size, small sample, and changes of data collection procedures