Brick and Tile Statistic Analysis
The question:
To investigate if there is evidence to suggest that the two operations brick and tile have a difference in accident rates.
This type of question involves analysing the data for a difference, and so tests such as an equal variance test, a normality test and a Mann Whitney test will be undertaken. The meaning and the significance of these tests will be explained and justified later on in the report.
Hypothesis Testing:
The null hypothesis (Ho) for this investigation is that there is no genuine evidence of difference in accident rates between the two operations. This hypothesis will be accepted if the p-value for the tests is greater than 0.05, otherwise it will be rejected and the alternative hypothesis (H1) will be accepted.
The p-value is the estimated probability of rejecting the null hypothesis (Ho) of a study when the study question is true (http://www.statsdirect.com/help/basics/pval.htm, 2009). The p-value of 0.05 is used as the main reference point for accepting or rejecting the null hypothesis, anything greater or smaller than 0.05 suggests the strength of evidence against, or for, the null hypothesis, as shown in table 1.
Table 1: Showing the range of p-values, action to take in that case and the strength of evidence it suggests. p-value | Action | Strength of evidence against Ho | >0.05 | Retain Ho | Insufficient | ≤0.05 | Reject Ho, Accept H1 | Some | ≤0.01 | Reject Ho, Accept H1 | Strong | ≤0.001 | Reject Ho, Accept H1 | Very strong |
As it can be seen from table 1, when a p-value is equal to or smaller than 0.05 the Ho must be rejected and the H1 accepted. The H1, for this investigation is that there is genuine evidence of difference in accident rates between the two operations. The Analysis: The analysis of the data was started by doing descriptive statistics for the data as shown below. Table 2: Showing the descriptive statistics for the brick and tile data. Variable N
To investigate if there is evidence to suggest that the two operations brick and tile have a difference in accident rates.
This type of question involves analysing the data for a difference, and so tests such as an equal variance test, a normality test and a Mann Whitney test will be undertaken. The meaning and the significance of these tests will be explained and justified later on in the report.
Hypothesis Testing:
The null hypothesis (Ho) for this investigation is that there is no genuine evidence of difference in accident rates between the two operations. This hypothesis will be accepted if the p-value for the tests is greater than 0.05, otherwise it will be rejected and the alternative hypothesis (H1) will be accepted.
The p-value is the estimated probability of rejecting the null hypothesis (Ho) of a study when the study question is true (http://www.statsdirect.com/help/basics/pval.htm, 2009). The p-value of 0.05 is used as the main reference point for accepting or rejecting the null hypothesis, anything greater or smaller than 0.05 suggests the strength of evidence against, or for, the null hypothesis, as shown in table 1.
Table 1: Showing the range of p-values, action to take in that case and the strength of evidence it suggests. p-value | Action | Strength of evidence against Ho | >0.05 | Retain Ho | Insufficient | ≤0.05 | Reject Ho, Accept H1 | Some | ≤0.01 | Reject Ho, Accept H1 | Strong | ≤0.001 | Reject Ho, Accept H1 | Very strong |
As it can be seen from table 1, when a p-value is equal to or smaller than 0.05 the Ho must be rejected and the H1 accepted. The H1, for this investigation is that there is genuine evidence of difference in accident rates between the two operations. The Analysis: The analysis of the data was started by doing descriptive statistics for the data as shown below. Table 2: Showing the descriptive statistics for the brick and tile data. Variable N
References: Dytham, C., (1999) Choosing and Using Statistics: A Biologist’s Guide. 1st ed. United Kingdom: Blackwell Science. Statistical Help from Stats Direct, 2009 P values [Online] (Updated 2009) Available at: http://www.statsdirect.com/help/basics/pval.htm