1. Part I

Studies have shown that hearing loss is related to the amount of noise pollution in cities. Suppose that researchers were interested in looking at the extent of hearing loss present among residents of Middelburg. To recruit participants they arrange a community event in which all residents can come to have a free hearing test. They obtain a very large sample of participants and measure their hearing as well as information on where they live and for how long. 

Among their conclusions are:

The participants had on average a higher level of hearing loss than the national average

The prevalence of hearing loss in Middelburg is higher than what is expected for cities of this size and level of development

1) Name the sampling strategy employed by the researchers.

2) Critically evaluate their conclusions in terms of external validity

3) Speculate on the types of people who would tend to be over or under-represented in the sample and describe the consequences this has for the external validity of this study.

 

  1. Part II

Consider the following:

According to the World Health Organization (WHO) environmental noise (e.g. from road traffic) is a leading environmental nuisance in Europe which can cause a number of health problems in populations ranging from cardiovascular effects to hearing impairment[1]

 

How loud is too loud?

The WHO guidelines for community noise recommend:

During the daytime, less than 35 A-weighted decibels dB(A) in classrooms to allow good teaching and learning conditions 

During the night: less than 30 (dB(A)) in bedrooms during the night for a sleep of good quality 

The WHO guidelines for night noise recommend less than 40 dB(A) of annual average (Lnight) outside of bedrooms to prevent adverse health effects from night noise.

Due to increased attention about the negative effects of noise and other forms of pollution on public health, many local governments are considering if and how they should account for this in their city planning, for example by creating more pedestrian only zones. 

 

To inform the local city government of Middelburg about the need for such strategies, you are to design a study to measure the amount of noise pollution residents are currently exposed to for comparison to the guidelines given by the WHO above. 

 

  1. Describe a sampling plan suitable for measuring (objective) noise in the city of Middelburg for inside bedrooms, inside classrooms or outside night noise (you choose). Include in your answer
    1. What is your procedure called (e.g. cluster, stratified, random, etc.)?
    2. Describe how it works.
    3. Explain why you have chosen this procedure over some of the alternatives? 
    4. Comment on external validity 
  2. Describe a sampling plan suitable for measuring the (subjective) annoyance levels residents report due to environmental noise
    1. What is your procedure called (e.g. cluster, stratified, random)?
    2. Describe how it works.
    3. Explain why you have chosen this procedure over some of the alternatives? 
    4. Comment on external validity