PSY173-Introduction to Psychological Research Methods

Task

A community living close to an industrial area has raised concerns about contaminants from industry causing health problems in local families.  Based on current research, the public health guidelines state that children should not have blood lead levels above 10 micrograms per decilitre, because elevated lead levels may cause long-term cognitive impairment.  

As part of the investigation, parents of all children in the 2- to 6-year-old age range who live within a 10km radius of the industrial area are contacted and strongly encouraged to have their children assessed. 

Lead levels in the children’s blood of are measured.  Blood samples are taken by a qualified phlebotomist at children’s homes.  A psychologist is employed to assess the children’s level of cognitive development.  Each child is assessed individually at the psychologist’s office, using a standardised developmental scale.  For each child, their attained score is compared to the score expected for children their age (in years and months), based on norms for the test gathered on a nationally representative sample of 200 children per age group in 2009.  A discrepancy score is calculated, which indicates how many months ahead of, or behind, the developmental norm for their age each child is.  Positive scores indicate being ahead of same-age peers.  Negative scores indicate developmental delay.   The table below shows the lead levels (in ?g/dL) of the 20 children tested and their developmental discrepancy scores (in months).

For statistical calculations, please round your final answers to two (2) decimal places.

A)What is the independent variable in this study?  What is the dependent variable in this study?  Explain your answer.

B)Complete the following table:  

Table 1.

C)Calculate the Mean, Standard deviation and Standard error of the mean for lead levels and development scores.

D)Calculate single sample t to compare the children’s lead levels to the recommended maximum of 10 micrograms per decilitre.  Calculate single sample t to compare the children’s developmental discrepancy scores to a mean of 0 (indicating normal rate of cognitive development). Complete the following table.  Please show your working on a separate sheet.

E)Write the results of the t-tests in APA format.

F)What conclusions would you feed back to the investigation about the lead levels of these children compared to the recommended maximum, and their level of cognitive development compared to the norm?

G)Draw a scatterplot showing the relationship between blood lead levels and developmental discrepancy scores. You may do this by hand on graph paper or using Excel if you prefer.

H.Calculate Pearson’s r for the association between blood lead levels and developmental discrepancy scores.  Complete the following table. Please show your working on a separate sheet. 

I) Write the result of this Pearson’s r in APA format.

J)From your calculation of Pearson’s r and your scatterplot, what conclusions would you report back to the investigation about the relationship between children’s blood lead levels and developmental delay? Indicate which specific observations lead you to these conclusion