= Variables Data Analyses Edit Paste Clipboard & ID Setup Compute 8 Low Oxygen Co Transform Edit Variables B & C 1 1 7 Low Oxygen 2 2 6 Low Oxygen 3 13 Low Oxygen 4 14 Low Oxygen 5 17 Low Oxygen 6 6 7 Low Oxygen 7 7 8 8 9 9 9 Control 10 10 15 Control 11 11 12 Control 12 19 Control 13 13 14 Control 14 14 14 Control 15 15 15 Control 16 16 13 Control 8 Low Oxygen Independent Samples T-Test & ID Tests Student's Bayes factor Prior 0.707 Welch's Mann-Whitney U Hypothesis O Group 1 Group 2 Group 1 Group 2 O Group 1 Group 2 Missing values INDEPENDENT SAMPLE T-TEST To do an independent sample t-test, our sampled values must all be in 1 column, and each row should represent only 1 case. We additionally have a grouping variable that labels to which sample each case belongs. E.g.: Researchers want to know if low oxygen environments alter one's ability to remember information. Researchers randomly assign individuals to complete a memory test either in a low oxygen environment (n = 8) or a normal environment (n = 8). Here the doctors can use an independent sample t-test. Q Dependent Variables -> Exclude cases analysis by analysis Exclude cases listwise > Memory Scores Grouping Variable a Oxygen Environment Additional Statistics Mean difference Confidence interval 95 % Effect size Confidence interval 95 % Descriptives Descriptives plots Assumption Checks Homogeneity test Normality test Q-Q plot To perform the independent sample t-test - the researchers would make the following selections in Jamovi. Notice how the researchers need to specify the dependent variable (memory score), their grouping variable (oxygen environment) and select the nature of their alternative hypothesis. Also notice that the researchers can obtain a 95% confidence interval around their point- estimate, descriptive statistics for their sample, a descriptives plot, and generate a Q-Q plot! This is what the results look like: Independent Samples T-Test Independent Samples T-Test Statistic df Mean difference SE difference Lower 95% Confidence Interval Upper Memory Scores Student's t -2.21 14.0 0.045 -3.88 1.76 -7.64 -0.107 Group Descriptives Group N Mean Median SD SE Memory Scores Low Oxygen Control 8 8 10.0 13.9 8.00 14.0 4.07 2.85 1.44 1.01 Standardized Residuals Memory Scores Memory Scores Low Oxygan Control Oxygen Environment Theoretical Quantiles Mean (95% CI) Median The researchers specifically want to make a Q-Q plot for each sample to make sure each is normally distributed. They go to the Exploration tab of Jamovi - and select "descriptives" and select the following options. For good measure they notice they can make a better graph (violin plot) to visualize the differences between the samples and select this option as well: Descriptives Descriptives Variables across columns > Statistics Plots Variables Memory Scores Split by a Oxygen Environment Histograms Box Plots Histogram Box plot Density Q-Q Plots Q-Q Label outliers Violin Data Jittered Mean Frequency tables Bar Plots Bar plot Memory Scores Memory Scores Low Oxygen Low Oxygen -1.5 1.0 0.5 0.0 0.5 Control Oxygen Environment Control 1.0 1.5-1.5 -1.0 -0.5 0.0 0.5 1.0 Theoretical Quantiles 7) Please perform an independent samples t-test by hand using output from this table and interpret the results. If there is a significant difference, make sure to interpret the point estimate relative to the null in the context of the hypothesis test.