Probability, Decision Making, The Planet, and You

Lefthanders in the Government

From a recent census we learn that 11% of the people who live in Argentina are left-handed. From this information, we can suppose that there is an 11% chance (or probability) that the next person we meet when we are in Argentina will be left-handed. Furthermore, we can suppose that if we were to conduct a survey with 200 participants in Argentina, about 22 out of those 200 are expected to be left-handed.

It has come to our attention through reading the research literature that there is generally a disproportionate amount of left-handed people working in certain jobs or occupations. For example, the percentage of individuals in official government positions who are left-handed is higher as compared to a country's general left-handed population. We don't know why, we just know it to be the case. We assume that this circumstance is true for government officals in Argentina as well.

Now suppose we are in Argentina's capital city of Buenos Aires. In fact, we are standing just outside the largest government office building in Buenos Aires, Argentina. Is the probability that the next person we meet will be left-handed still 11%? Would you belive that the probablity is higher that 11%, maybe somewhere around 15% or even 20%! How this is possible? Well, this is the case because there are likely to be more left-handers near government office buildings in Buenos Aires, Argentina relative to the general population of Argentina.

In the same sense, if we were to conduct a survey near such government office complexes in Buenos Aires, Argentina we would also expect the number of left-handers to be appreciabley higher than 22 among 200 participants. Do you see how this is possible? See if you can use the information just presented in answering the following exercises.

Exercises

At present, the country of Argentina is experiencing a great influx of immigrants from Asian countries. In the following exercises, assume that 9% of the total population of Argentina is accurate for people that identify themselves as being Asian (on census forms, questionnaries, etc.)

Exercise 1

In a random sample of 300 adults in Argentina how many would you expect to identify themselves as being Asian?

 

Exercise 2

Same question for a random sample of 300 adults in Buenos Aries.


Exercise 3

Suppose that you had information about 2000 citizens sampled from lists of people called to jury service in Argentina. Once you have the data in hand, you notice that 92 of them were identified as Asian. Would you conclude that Asians living in Argentina are underrepresented among those called to jury service?

 
 

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