Judgements of likelihood under hypoxic conditions (descriptive statistics) - 2010

[ROBINSON Melissa [ed] & Jose D PEREZGONZALEZ [ed] (2012). Judgements of likelihood under hypoxic conditions (descriptive statistics). Journal of Knowledge Advancement & Integration (ISSN 1177-4576), 2012, pages 271-274.] [Printer friendly]

Mild hypoxia and optimistic judgement

Gilbey et al (20101) carried out a pilot study for ascertaining whether mild hypoxia2 led to more optimistic (or pessimistic) judgements about the likelihood of certain life events3 than otherwise. This article provides detailed descriptive information about the results of that research.

Results showed that a small group of participants only slightly changed their judgements about life events between normal and hypoxic conditions (see illustration 1). Many of these changes can be considered negligible, although some small changes were also observed. Statistically speaking, the latter changes showed standardised effect sizes ranging between small (delta=0.226) and medium (delta=0.40) for five judgments. However, such effect sizes may not reflect a similarly important difference in scores between conditions. After all, the participants estimated their judgements of likelihood on a Likert scale. If we take each anchor as the centroid for a particular estimate of likelihood (eg, '5, Lightly above average'), it is reasonable to assume that such estimate actually ranges midway between the immediately lower and upper anchors (eg, any score between 4.5 and 5.4 would be considered 'Lightly above average'). Thus, a change of 0.5 points on this scale (ie, a change that moves an estimate from a centroid to the next range) may be a reasonably minimum degree of change expected before considering such change as something noteworthy4. Following this logic, then, most of the differences between conditions among these participants were below such threshold and, thus, rather unimportant.

Illustration 1: Results obtained under normal and hypoxic conditions
Normoxia Hypoxia Difference5 Delta6
Overall judgement of likelihood 5.46 5.43 -0.03 -0.05
Items included in group analysis
Normoxia Hypoxia Difference5 Delta6
Maintaining good relationships with relatives 5.40 5.80 0.40 0.44
Staying healthy and fit to an old age 5.27 5.67 0.40 0.33
Not being fired from a job 4.87 5.27 0.40 0.35
Falling or staying in love 5.73 5.40 -0.33 -0.34
Not becoming sterile 5.00 4.67 -0.33 -0.25
Not developing a drinking problem 5.80 5.53 -0.27 -0.22
Not attempting suicide 6.47 6.40 -0.07 -0.09
Having a successful career 5.33 5.40 0.07 0.06
Not having a heart attack before 40 5.27 5.20 -0.07 -0.05
Traveling extensively 5.20 5.27 0.07 0.06
Liking my job 5.20 5.13 -0.07 -0.06
Not getting infected with Aids 5.67 5.73 0.06 0.05
Items excluded from group analysis7
Living beyond 80 --- --- --- ---
Getting a wonderful surprise next birthday --- --- --- ---
Not contracting cancer --- --- --- ---
Not being a victim of theft --- --- --- ---
(Mean values on a 1-7 Likert scale; values above 4 represent "optimism")

Regarding grouped values, there are some considerations to take into account in order to interpret them correctly. On the one hand, the authors separated items which showed a statistically significant difference from '4, Average' from those which did not show such statistical difference. They then added up the former as if they represented a measure of 'unrealistic optimism' while excluding the others. This is a questionable practice if all items ever contributed to such measure of 'unrealistic optimism', as there should not be any provision for "cherry-picking" those items which provide good results from those which do not. Thus, the grouped results are meaningless under the assumption that the selected items (but not the others) measured either 'risk judgement' or 'unrealistic optimism'.

On the other hand, the grouped results may be valuable if we consider them simply as judgements of likelihood about selected life-events. In this case, "cherry-picking" is a plausible strategy as a way of describing a change in judgements which were already biased in this particular group of participants (ie, it may not be adequate to generalise to other judgements, life-events or groups). Under this assumption, it is appropriate to interpret changes between conditions, which, for this particular group, were negligible (delta=-0.05), most probably due to the adding up of items which diverged from average in either direction, thus balancing their differences out.


Melissa ROBINSON (2012). Massey University, New Zealand. melissa robinsonmelissa robinson
Jose D PEREZGONZALEZ (2012). Massey University, Turitea Campus, Private Bag 11-222, Palmerston North 4442, New Zealand. (JDPerezgonzalezJDPerezgonzalez).

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