Study Design Flashcards

1
Q

double blind

A

both experimenter and subjects are blinded

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2
Q

crossover study

A

Each study participant receives all treatments that are being investigated but at different times

Order of treatments is randomized

Washout often included between treatments

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3
Q

partial crossover or incomplete block

A

In some crossover designs, particularly ones with more than 2 treatments, patients may not receive all treatments under investigation, but would receive more than 1

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4
Q

Pros of Crossover Study Design

A

Each patient serves as their own control.

Reduces between-subject variability.

Allows for detection of smaller effect sizes with reduced sample sizes.

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5
Q

Effect Size

A

Quantitative measure of the magnitude of a phenomenon (eg. the correlation between 2 variables)

Small effect size is one in which there is a real effect, i.e. something is really happening in the world - but which you can only see through careful study.

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6
Q

Parallel Study

A

Two groups of treatments: A & B

One group receives only A, other group receives only B

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7
Q

Longitudinal Study

A

Repeated observations of the same variables over short or long periods of time.

Often observational but can be structured as longitudinal randomized experiments.

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8
Q

Large Effect Size

A

Can be seen by the naked eye, easily observed.

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9
Q

Small Effect Size

A

There is a real effect, i.e. something is really happening in the world - but which you can only see through careful study.

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10
Q

Confounders

A

Variable that influences both dependent and independent variables.

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11
Q

Why is the influence of confounders reduced in crossover studies?

A

Each patient is their own control.

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12
Q

Optimal crossover designs require ________ subjects.

A

fewer

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13
Q

Which patient population best aligns with crossover study design?

A

Crossover studies are often done to improve symptoms of patients with chronic conditions.

May be infeasible or unethical for curative treatments or rapidly changing conditions.

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14
Q

What are two main issues with crossover studies?

A
  1. “Order” Effects. Order of treatment may effect outcome, eg. drug with many adverse effects given first, making patients taking a 2nd, less harmful medication, more sensitive to any adverse effects.
  2. “Carry-over”. Carry-over between treatments which confounds estimates of treatment effects. In practice “carry-over” effects can be avoided with a sufficiently long “wash-out” period between treatments. However, planning for sufficently long wash-out periods requires expert knowledge of the dynamics of the treatment, which is often unknown.
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