Dyslexia refers to a specific reading disability that affects 10% to 15% of the general population. A dyslexic child is defined as a child of normal or above-normal intelligence with no known organic behavioural disorders who, despite normal schooling, shows a reading lag of at least two years. A researcher proposed that dyslexia was the result of a complex visual deficit that could be immediately corrected by simply putting a blue plastic overlay on the reading material. To test this, 100 dyslexic children were randomly assigned to one of two groups, one of which read from pages with a clear plastic overlay an
Dyslexia refers to a specific reading disability that affects 10% to 15% of the general
population. A dyslexic child is defined as a child of normal or above-normal intelligence
with no known organic behavioural disorders who, despite normal schooling, shows a
reading lag of at least two years. A researcher proposed that dyslexia was the result
of a complex visual deficit that could be immediately corrected by simply putting a blue
plastic overlay on the reading material. To test this, 100 dyslexic children were
randomly assigned to one of two groups, one of which read from pages with a clear
plastic overlay and the other of which read from pages with a blue plastic overlay. The
dependent variable was percentage correct on a multiple-choice reading
comprehension test.
a) Is this an observational study or an experiment? Explain your choice.
b) Why did the researcher use a clear overlay as one of the treatment groups
instead of just having the children read the passage without an overlay?
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