Data analysis Part 9: Why t test is required, can we use mean and standard deviation instead?        Looking at mean and standard deviation it is difficult to predict conclusively whether the parameter (weight, marks) of two batches of sample really represents same mean or not.  Two sample t test provide statistically valid decision making capability.   Decision making becomes bias free from individual . Decision making is done usually with 95% confidence level if we select α = 0.05.

Data analysis Part 8: Two sample t test with unequal variances (Welch’s t-test) Two sample t test is done to decide if the population mean of two batches of samples are is equal or not.  Population mean of two batches of samples are equal or not? To perform two sample t test with unequal variances, first F test is carried out to find out whether the variances of the two samples are equal or not. Let us take two sets of data as follows (Actual weight of paracetamol tablets that are marketed as 500mg) Batch1 Batch2 499.643 500.240 499.475 501.055 500.459 500.120 499.692 500.680 497.946 500.478 500.280 500.157 500.072 499.961 500.054 500.833 499.619 501.052 500.761 499.996 499.251 499.264 500.808 499.221 500.224 500.384 500.083 500.999 500.747 499.507 498.547 500.690 501.282 499.731 499.672 499.934 499.086 497.957 499.600 499.131 500.828 499.257 501.772 502.237 499.615 498.184 500.491 500.381 499.105 501.112 Result of F test sug...