In 1998, Emily Rosa et al. published an article in JAMA “investigat[ing] whether

Question

In 1998, Emily Rosa et al. published an article in JAMA “investigat[ing] whether TT [Therapeutic Touch] practitioners can actually perceive a ‘human energy field.’ … practitioners … were tested under blinded conditions to determine whether they could correctly identify which of their hands was closest to the investigator’s hand. Placement of the investigator’s hand was determined by flipping a coin.” If TT practitioners could not detect a human energy field, their chance of guessing correctly would have been 0.5.

A total of 280 trials were conducted. What is the smallest number of correct guesses that would have to be made in order to provide “statistically significant” (p < 0.05) evidence that practitioners could detect a human energy field?

146

155

163

168

173

146

155

163

168

173

Explanation / Answer

We use here binomial distribution to find the probability.

n= taotal number of trials =280

P=TT practitioners could not detect a human energy field, their chance of guessing correctly would have been 0.5.

P=0.5

X= human energy field

1) X= 146

   Using excel we compute this probability.

=BINOM.DIST(146,280,0.5,0)

=0.036869    < 0.05 Statistically significant

2) X = 155

=BINOM.DIST(155,280,0.5,0)

=0.009575     < 0.05 Statistically significant

3) X=163

=BINOM.DIST(163,280,0.5,0)

=0.001085     < 0.05 Statistically significant

4) 168

=BINOM.DIST(168,280,0.5,0)

=0.000173    < 0.05 Statistically significant

5) 173

=BINOM.DIST(173,280,0.5,0)

=0.0000190   < 0.05 Statistically significant

Comment -173 is smallest number of correct guesses that would have to be made in order to provide “statistically significant” (p < 0.05) evidence that practitioners could detect a human energy field.

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