All are true regarding students t-test, except ?

Ans. is 'a' i.e., Standard error of mean is not calculated Student t test o Small samples do not follow normal distribution as large ones do. To overcome this problem 't' test was devised by W.S. Cassette whose pen name was 'student' and hence this test was called student 't' test. Application of test : o It is applied to find the significance of difference between two means, when sample size is less than 30. o It is applied on a standard population either as : 1. Unpaired 't' test : Applied when data is unpaired, i.e. when separate observations are made on inidividuals of two separate groups, and these need to be compared : Null hypothesis is assumed Observed diference between means of two samples is found. Standard error or difference between two means is calculated. t value is estimated. This is the ratio between points 2 and 3. Degrees of freedom are next calculated Calculated values are compared with the 't' table values at the calculated degree of freedom (option d) P values are obtained and if it is more than 0.05, it has no significance. 2. Paired test : Is applied to paired data, when each individual gives a pair of observations such as : when observations are made before and after the play of a factor e.g. pulse rate before and after a drug. Fuher, it proceeds similar to the unpaired test.