Significance test of group mean differences Welch’s t-test was carried out on each pair of comparable group of seasonal workers and working holiday makers to see whether the mean productivity of seasonal workers was statistically different to the mean productivity of working holiday makers. The test is: where and are the unobserved group mean productivity of seasonal workers and working holiday makers respectively and the test assumes that the population variance in each group can be different. This study is interested in testing the null hypothesis that the two group means are the same, against the alternative hypothesis that seasonal workers have higher mean productivity than working holiday makers (one-sided test). Table 10 shows the results of Welch’s t-test across our sample dataset. In all cases except the berry farm, Welch’s t-test rejected the null hypothesis at the 10 per cent significance level. Table Welch t-test statistics for seasonal workers and working holiday makers Grower ID Financial Number of Average Welch t-test year workers productivity ($/hour) SW WHM SW WHM Test Degrees statistic freedom 2013–14 Citrus 25 11 24.4 21.7 1.75 15.1 0.05 Grower A 2014–15 Citrus 44 23 25.7 21.6 3.95 53.5 0 2015–16 Citrus 44 39 26.8 20.4 6.18 75.4 0 Grower B 2015–16 Berries 25 25 23.7 23.4 0.14 41.8 0.45 Grower C 2015–16 Citrus 12 11 32.5 23.7 11.5 16.6 0 Note: SW denotes seasonal workers; WHM denotes working holiday makers Source: ABARES
Significance test of group mean differences Welch’s t-test was carried out on each pair of comparable group of seasonal workers and working holiday makers to see whether the mean productivity of seasonal workers was statistically different to the mean productivity of working holiday makers. The test is: where and are the unobserved group mean productivity of seasonal workers and working holiday makers respectively and the test assumes that the population variance in each group can be different. This study is interested in testing the null hypothesis that the two group means are the same, against the alternative hypothesis that seasonal workers have higher mean productivity than working holiday makers (one-sided test). Table 10 shows the results of Welch’s t-test across our sample dataset. In all cases except the berry farm, Welch’s t-test rejected the null hypothesis at the 10 per cent significance level. Table Welch t-test statistics for seasonal workers and working holiday makers Grower ID Financial year Number of workers Average productivity ($/hour) Welch t-test SW WHM SW WHM Test statistic Degrees freedom 2013–14 Citrus 25 11 24.4 21.7 1.75 15.1 0.05 Grower A 2014–15 Citrus 44 23 25.7 21.6 3.95 53.5 0 2015–16 Citrus 44 39 26.8 20.4 6.18 75.4 0 Grower B 2015–16 Berries 25 25 23.7 23.4 0.14 41.8 0.45 Grower C 2015–16 Citrus 12 11 32.5 23.7 11.5 16.6 0 Note: SW denotes seasonal workers; WHM denotes working holiday makers Source: ABARES
whatdifflabourchoice_20180206_v1.0.0.docx