GDO Oral Recit Flashcards
(6 cards)
What are the key components of factorial design?
The key components of a factorial design are factors, which are the independent variables being investigated, and their levels, representing the specific settings or categories for each factor.
The experiment then involves testing every possible combination of these factor levels to observe their effects on a response variable (the dependent variable).
What is the difference between Tukey’s HSD and Tukey-Kramer test?
Tukey’s HSD (Honestly Significant Difference): This test is specifically designed for situations where all group sample sizes are equal. It uses a single critical value for all pairwise comparisons.
Tukey-Kramer Test: This is a modification of Tukey’s HSD that allows for comparisons when group sample sizes are unequal. It adjusts the critical range calculation for each pairwise comparison to account for the differing sample sizes, making it more robust.
What is the difference between post hoc testing and planned experimental comparison?
Planned experimental comparisons are specific comparisons decided before data collection, based on strong theoretical hypotheses.
In contrast, post hoc testing is performed after an overall significant result (e.g., from an ANOVA) to explore which specific group differences are significant.
Post hoc tests are more exploratory and adjust for the increased risk of false positives that comes with making many comparisons.
What is post hoc testing and why is it important to analytical chemistry?
Post hoc tests then pinpoint which specific pairs or combinations of groups are significantly different from each other.
It’s important in analytical chemistry because chemical experiments often involve comparing multiple methods, samples, or conditions (e.g., different analytical techniques, varying reagent concentrations, or multiple batches of a product). Without post hoc testing, a chemist might know there’s a difference in analytical results but wouldn’t know which specific comparisons are driving that difference, leading to inconclusive findings.
What is Tukey’s test and how is it used in analytical chemistry?
Tukey’s test (HSD) is a post hoc statistical tool used after ANOVA to identify specific group mean differences when an overall difference is found. It’s crucial in analytical chemistry for comparing multiple methods or conditions.
This helps chemists make confident decisions about experimental design and process optimization by pinpointing exact differences among groups.
Can you provide an example of how both randomization and blocking are applied in a chemometric study?
Scenario: Comparing four extraction methods (A, B, C, D) for a compound from plant samples, where samples come from different locations.
Blocking: Group samples by their location (e.g., all samples from Farm 1 together). This accounts for known differences that location might cause.
Randomization: Within each location group, randomly assign which sub-sample gets which extraction method (A, B, C, or D). This spreads out any unknown variations, ensuring a fair test of the extraction methods.
