t-Test for Two Independent Samples - The Diigo Meta page

• 29 Jun 11
  

  Scott Stein

  statistics imported 2_11_06 science fairs_statistics

• 28 Feb 11
  

  Elliot Rapp

  Research Peripheral CTA

• 12 May 10
  

  Serena Magrogan

  ap biology teach lab

• 21 Feb 10
  

  Jan Schubert
  • In each of these cases, the two samples are independent of each other in the obvious sense that they are separate samples containing different sets of individual subjects. The individual measures in group A are in no way linked with or related to any of the individual measures in group B, and vice versa. The version of a t-test examined in this chapter will assess the significance of the difference between the means of two such samples, providing: (i) that the two samples are randomly drawn from normally distributed populations; and (ii) that the measures of which the two samples are composed are equal-interval.
  • ¶Logic and Procedure 
    
     The groundwork for the following points is laid down in Chapter 9. 
    
      

    (1)	The mean of a sample randomly drawn from a normally distributed source population belongs to a sampling distribution of sample means that is also normal in form. The overall mean of this sampling distribution will be identical with the mean of the source population:

      

    iM  =  isource

    From Ch.9, Pt.1

      

    (2)	For two samples, each randomly drawn from a normally distributed source population, the difference between the means of the two samples,   Ma—Mb   belongs to a sampling distribution that is normal in form, with an overall mean equal to the difference between the means of the two source populations

       

    iM-M  =  isource A — source B

    From Ch.9, Pt.1

     
      

    (2)	On the null hypothesis, isource A and isource B are identical, hence

      

    iM-M  = 0

       

    (3)

    For the present example, the null hypothesis holds that the two types of music do not have differential effects on task performance. This is tantamount to saying that the measures of task performance in groups A and B are all drawn indifferently from the same source population of such measures. In items 3 and 4 below, the phrase "source population" is a shorthand way of saying "the population of measures that the null hypothesis assumes to have been the common source of the measures in both groups."
• 30 Jun 09
  

  Kate Reid

  t-test statistics

• 30 Mar 08
  

  Eric Hileman

  research statistics tutorial T-test SPSS

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