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What did the Seychelle child development study want to look for? What did they find instead?

Researchers were looking for association between pre-natal mother mercury exposure and children development
Found no association after 6 months
66 months: Benefits were found between mercury and developmental outcomes (probably due to benefits of FISH (omega 3s) outweighing the risks of MERCURY.)


Why did populations who eat +++ pilot whales had detrimental effects of mercury?

Because selenium is found in lower quantities in pilot whales.


What are the 4 types of fish/shellfish most consumed in Canada and US?

1. Shrimps
2. Salmon
3. Tuna
4. Sardines
Main message: Knowing where the data is coming from is key.


Who is at risk of +++ mercury?

Pregnant women, children, people who rely on fish as their main source of nutrition (around 1 M people worldwide)


Where is most of the research evidence coming from?

High-income countries (Canada, US, europe...). Results may not apply to lower income countries


Which nutrients in fish make it good for you?

Protein, selenium, omega 3s (LCFAs), Vitamin D, iodine


What makes fish healthy?

Not only the nutrients but the act of fishing (relaxation) and fight against FI. Not just about the molecules inside the fish but what fish means to people


What are the main food sources of omega 3s?

Nuts and seeds


What are the causal links between omega 3s and IQ?

omega 3s (molecule) first affect the cell which comprise tissues, which comprise organs, which comprise individuals and a group of individuals make up the population


What makes fish bad for you?

Mercury, bacteria, PCBs, mislabelled fish
Sustainability aspect of overfishing?


Name 2 events in which mercury was a problem

Japan 1940s to 1950s - industry fed the bay with mercury... belief that "Dilution is a solution to pollution"
Grassy Narrows (first nation reserve) was fishing from a water full of mercury from industry


What proportion of women of childbearing age have too much mercury in their body?

1 in 6 women of childbearing age have mercury levels in their body that might be high enough to cause effect in a child


Explain the example of mercury and IQ levels on individuals vs. the population

If mercury in fish makes our IG go down by 5 points, we couldn’t be able to tell individually
If it does that for the whole population, we will notice: the 5% that is gifted with a high IQ will half
Why would you be able to tell on a population level? Reduce human potential, will put strain on society. Little changes matter.


Differentiate qualitative vs quantitative variables

Qualitative variables: Properties that vary in a type of attribute (Ex. Sex, religion, eye color, marital status, type of fish consumed)
Quantitative: Properties that differ in an amount (Ex. height, weight, BP, Number of servings of fish per week)


Differentiate discrete vs continuous variables

Discrete: Quantitative adjacent variable in which no intermediate values are possible (E.g. number of children)
Continuous: Intermediate values are possible in between two adjacent scale values (E.g. height, weight, BP)
But in practice, these are usually converted into discrete variables


Differentiate between independent and dependant variables

Independent variable (X): Presumed causal factor in a cause-effect relationship. Exposure, intervention, treatment, diet…
In an experiment, this is what you manipulate (X-axis)
Dependent variable (Y) – outcome; Presumed effect in a cause-effect relationship; "depends” upon the independent variable
In an experiment, this is the outcome you measure (Y axis)


What is a variable?

A factor or attribute that can assume two or more values


What is a domain? What is the smallest possible domain?

All possible values a variable can have
Smallest domain is 2 (dichotomous or binary)


What is a mediator variable? Provide examples for Fish consumption --> IQ.

Variable to explain why X and Y are liked… Provides the CAUSAL link
Fish consumption --> Omega 3 content, protein content, selenium content, iodine content --> IQ (+)
Omega 3 --> neural cells --> increased neural function/brain health etc…
Fish --> omega 3 --> cell --> tissue --> individual --> IQ


What is a moderating variable? Provide examples for fish consumption --> IQ.

(X --> Y) * moderator (M)
Variable that alters the strength or direction or the relationship (Aka interaction terms)
For fish: E.g. health status, genetics, sex, age, life stage

A moderator can also be a confounder


What is a confounding variable? Give an example for fish consumption and IQ

Variable (C) that correlates with both X and Y; Not in the causal pathway but causes confusion in the true relationship

E.g. education level (more education = more money to get fish, more education = more knowledge about benefits of fish, …)


Suppose there is a statistical relationship between ice cream consumption and drowning
What could be a mediator variable?
What could be a confounding variable?

Mediator: none
Confounding: Temperature, age


Discuss the transfer of conceptual variables into operational.

Scientists need to be explicit on how they define their variables
Conceptual variables are the “ideas”
Must provide operational definitions AND how to measure these (method? Valid?)
Scientists can disagree on how to define certain variables (IQ? CVD?)
Disagreements can be frustrating… Can lead to poor decisions… may lead to debate and progress


What are the 4 Stevens Scales of measurement?

Nominal, ordinal, interval, ratio


Define the nominal scale and give examples.

Qualitative differences in scale value
e.g. sex, politics, college major, food categories, hair color...
Cannot be ordered


Discuss the accuracy of food labels study

• Covered under US code of federal regulations
• Scientists measured energy content in 24 snack foods purchased from a single grocery in phoenix on 3 occasions in 2010
• One serving size was based on the label, and then energy content measured via bomb calorimetry
Among a convenience sample of energy‐dense snack foods, caloric content is higher than stated on the nutrition labels, but overall well within FDA limits. This discrepancy may be explained by inaccurate carbohydrate content and serving size.


Define the ordinal scale and give examples.

Different scale values represent relative differences and the order matters
e.g. likert scales, apgard score, rank ice cream preferences
> or


Define the interval scale and give examples.

Scale values have an equal and exact distance
e.g. temperature, time of day, calendar year
+ or -


Define the ratio scale and give examples.

Interval but has an absolute zero
e.g. length, annual income, caloric intake, pregnancies, money
x or ÷


Define accuracy, and what bad accuracy can be attributed to.

The degree to which the measurement yields results that agree with the truth. How do you know the measurement is valid? Usually not. Measurements are proxies.
Can be d/t systemic error in the instrument, calibrating error, placement error...

Able to reproduce results?