Hi
Paul's observations were intriguing. One thing to note is that the p
value for the Message main effect is .1128 for F(1, 34) = 2.65. So very
close to significance by a directional test (i.e., one assuming the
priming effect mentioned by Paul). It was simply reported as ns in the
paper, without a p value.
So as to analyze something like the original paper's data more fully, I
generated some values very close to those in the paper, except that I
did not have unequal Ns. I used n = 7 per cell to keep fairly close to
the df error from the original study. Here is the hypothetical data and
the descriptive statistics. I hope the formatting does not get too
messed up below (like it just did when I unwisely switched between text
and html mode).
data list free / mess hurr help.
begin data
1 1 1 1 1 5 1 1 5 1 1 4 1 1 2 1 1 5 1 1 5
1 2 1 1 2 3 1 2 3 1 2 0 1 2 0 1 2 5 1 2 2
1 3 0 1 3 0 1 3 0 1 3 1 1 3 4 1 3 0 1 3 2
2 1 0 2 1 4 2 1 4 2 1 2 2 1 0 2 1 0 2 1 2
2 2 3 2 2 2 2 2 0 2 2 5 2 2 0 2 2 0 2 2 2
2 3 0 2 3 0 2 3 0 2 3 0 2 3 0 2 3 0 2 3 4
end data.
glm help by mess hurr /print = descr.
mess hurr Mean Std. Deviation N
1 1 3.86 1.676 7
2 2.00 1.826 7
3 1.00 1.528 7
Total 2.29 2.004 21
2 1 1.71 1.799 7
2 1.71 1.890 7
3 .57 1.512 7
Total 1.33 1.742 21
Total 1 2.79 2.007 14
2 1.86 1.791 14
3 .79 1.477 14
Total 1.81 1.916 42
The cell means (above) and MSE (below) are very close to those in the
published paper, although the column means in particular are off because
of the unequal Ns in the paper. The following analysis shows more robust
effects than the analysis in the paper, presumably because of the
unequal Ns analysis they did. Note the message effect now has p = .08,
which would be significant by a directional test.
Source Type III Sum of df Mean Square F Sig.
Squares
Corrected Model 45.048(a) 5 9.010 3.076 .021
Intercept 137.524 1 137.524 46.959 .000
mess 9.524 1 9.524 3.252 .080
hurr 28.048 2 14.024 4.789 .014
mess * hurr 7.476 2 3.738 1.276 .291
Error 105.429 36 2.929
Total 288.000 42
Corrected Total150.476 41
I then wondered what a simple effects analysis would show even though
the interaction does not appear to be significant, p = .291, given
interaction terms are notoriously insensitive to non-cross-over
interactions. The simple effect of message at different levels of hurry
produced a significant difference for the No Hurry condition, p = .025.
manova help by mess(1 2) hurr(1 3)
/design hurr mess w hurr(1) mess w hurr(2) mess w hurr(3).
Source of Variation SS DF MS F Sig of F
WITHIN+RESIDUAL 105.43 36 2.93
HURR 28.05 2 14.02 4.79 .014
MESS W HURR(1) 16.07 1 16.07 5.49 .025
MESS W HURR(2) .29 1 .29 .10 .757
MESS W HURR(3) .64 1 .64 .22 .642
And the simple effect of hurry at each level of message produced only a
significant simple effect for the helping message condition, which was
due to the linear decrease in helping, but no significant effect for the
no hurry condition.
manova help by mess(1 2) hurr(1 3) /print = sign(single)
/contrast(hurr) = polynomial
/design mess hurr w mess(1) hurr w mess(2).
Source of Variation SS DF MS F Sig of F
WITHIN+RESIDUAL 105.43 36 2.93
MESS 9.52 1 9.52 3.25 .080
HURR W MESS(1) 29.43 2 14.71 5.02 .012
1ST Parameter 28.57 1 28.57 9.76 .004
2ND Parameter .86 1 .86 .29 .592
HURR W MESS(2) 6.10 2 3.05 1.04 .364
1ST Parameter 4.57 1 4.57 1.56 .220
2ND Parameter 1.52 1 1.52 .52 .475
These (hypothetical) results are probably more interesting than the
original conclusions. The interaction demonstrates the power of the
situation (urge to hurry) to nullify the priming effect of having
thought about the Good Samaritan.
I now have another good example to illustrate the analysis of factorial
studies, but the more fundamental question, as Paul notes, is whether
any researchers have replicated this study and what they found.
Take care
Jim
James M. Clark
Professor & Chair of Psychology
204-786-9757
204-774-4134 Fax
[email protected]
>>> Paul C Bernhardt <[email protected]> 31-Oct-12 9:58:13 PM
>>>
So, back to work finally. I'm preparing my lecture for Social
Psychology tomorrow. Revising my old Helping lecture to fit only one day
because of lost days to the storm. I'm reviewing in detail on the Darley
and Batson study from 1973 that showed seminary students became unlikely
to help an apparently ill stranger when put under time pressure, even if
they'd just written a sermon based on the parable of the Good Samaritan.
I wanted some details so I found the published study and wow... wow* so
much to question to my eye: erroneously applied randomization of
procedures making for unequal Ns and no indication of what the Ns were
in the conditions, weak statistical methods (though possibly state of
the art for the time).
One of the main findings is that preparing the sermon on the parable
did not increase helping compared to creating a sermon on another topic.
But, looking at the results, it looked to me like there was evidence for
helping having increased for those who prepared the Good Samaritan
sermon. And, I found a later critique suggesting the analysis looked
wrong. This is a very popular study to teach in undergraduate classes
and it doesn't fit well, IMO, with the large body of work supporting
priming a cognitive schema, in this case for helping (the type of sermon
written should have done that).
Given the level of importance this is given in some textbooks, has
there been any replications that would support the lack of finding an
effect for activation of a helping schema?
You might enjoy reading the study.
http://www.ssc.wisc.edu/~omirosa/357/Readings/13-Darley_and_Batson.pdf
Paul
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