Posted by: tonyteaching | May 29, 2011

Difference analysis (T test) using Excel 2007

Toolkitpak Installation sequence:

excel 2007excel 2007

excel 2007

CLICK GO:

2007 T Test:

  • Go to the DATA ribbon
  • Select the DATA ANALYSIS MENU (below)

  • Select the data ranges and set the alpha (critical P) level:

Excel 2007 results sheets:

ttest result

Writing a conclusion:

We can see the analysis from 2 parameters:

option 1 : P (T<=t) two-tail

We reject H0 if “P (T<=t) two-tail” < critical P level (commonly 0.05)
Option 2: t Stat

We reject H0 if t Stat is not in range of -(t Critical two-tail) and +(t Critical two-tail)

on the example above,

tStat is= – 4.54 . it is out of range between t critical two-tail (- 2.1 up to 2.1) so we reject the H0 …so …There is a significant deferent

or

P (T<=t) two-tail = 0.0003 and this value is < 0.05 so we reject H0

*******************************************

The results of the dependent t-test can be seen in the resultant table. The value of t (t Stat) is -4.53744, which we can round off to -4.54.

The probability of this result being due to chance can be read from the table as 0.000291 (two-tail) which means that this result is significant at the .0003 level.

We will set our alpha level as .05, so we will say that p < .05 rather than that p = .0003.

We could also look up the t critical value or cut-off value for t from the table by looking at t Critical one-tail which is 2.110 without using the spreadsheet.

We now have all the information we need to complete the six step statistical inference process:

  1. State the null hypothesis and the alternative hypothesis based on your research question.
    Null hypothesis: There is no significant difference between the height of the two samples of snail shells.
    Alternative hypothesis: There is a significant difference between the height of the two samples of snail shell.
  2. Set the critical P level (also called the alpha level )
    P=0.05
  3. Calculate the value of the appropriate statistic. Also indicate the degrees of freedom for the statistical test if necessary.
    t = -4.53
    df = 17 (unpaired , unequal sample variance)
  4. Write the decision rule for rejecting the null hypothesis.
    Reject null hypothesis since t is <= -2.110
  5. Write a summary statement based on the decision.
    Reject null hypothesis , p < .05, two-tailed
  6. Write a statement of results in standard English.
    There is a significant difference between the height of snail shells in the two samples.

Responses

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