# The stimulant Ritalin has been shown to increase attention span and improve academic performance in children with ADHD (Evans et al., 2001). To demonstrate the effectiveness of the drug, a researcher selects a sample of n = 20 children diagnosed with the disorder and measures each child’s attention span before and after taking the drug. The data show an average increase of attention span of MD= 4.8 with a variance of s2 = 125 for the sample of difference scores. Is this result sufficient to conclude that Ritalin significantly improves attention span? Use a one-tailed test with α = .05.

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1. The stimulant Ritalin has been shown to increase attention span and improve academic performance in children with ADHD (Evans et al., 2001). To demonstrate the effectiveness of the drug, a researcher selects a sample of n = 20 children diagnosed with the disorder and measures each child’s attention span before and after taking the drug. The data show an average increase of attention span of MD= 4.8 with a variance of s2 = 125 for the sample of difference scores. Is this result sufficient to conclude that Ritalin significantly improves attention span? Use a one-tailed test with α = .05.
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Step 1

It is given that the difference of means is 4.8 and variance is 125. The sample size is 20. The level of significance is 0.05.

Null hypothesis:

µ=0.

Alternative hypothesis:

µ>0.

This is a right tailed test.

The test statistic value can be obtained as follows:

Step 2

Computation of P-value:

The P-value of t-distribution at 19 degrees of freedom can be obtained using the excel formula “=T.DIST.RT(1.92,19)”.

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