Results and
Discussion
Let’s discuss this assignment!
Find 1 person to work with and
move your desks together
O Take out the paper that you turned in (I
returned them to you in your folder today).
O Make sure that at least one of you has the
assignment sheet and grading rubric.
O Read through the assignment sheet and
write down in your research notebook (left
side) anything (words, or concepts) from the
assignment that you are unclear about.
Start with experimental
design…
O First, can you explain exactly what you did in
your experiment?
O What was your IV? Did you have multiple IVs?
O What was your DV?
O How many trials did you perform?
O Based on your background research (take a
look at that paper too!), what would you
expect to happen in your experiment?
O What were your null and alternate
hypotheses?
Now let’s look at the data…
O What trends do you notice in your RAW
data? How does this compare to what you
expected to happen?
O How do your descriptive statistics (mean,
median, mode, range, variance and
standard deviation) describe your data?
O What is your p-value? What does the pvalue tell us?
Logic of Statistical Testing
O Inferring from samples – INFERENTIAL STATISTICS
O Scientists collect data from a sample and determine
whether or not that sample provides EVIDENCE
AGAINST the null hypothesis.
O If the null hypothesis is true, what is the probability we
would have randomly chosen a sample with the values
we observed?
O Analysis:
O By looking at our probability of obtaining 80% or 8
heads in a sample of 10 flips, we can make a
decision.
O PROBABILITY IS OFTEN CALLED THE P value
Statistical Significance
O Need a cut point for the p-value
O Common “cut points”: 0.05, 0.01, .001
O If P value < 0.05,
•
you say the result is “statistically significant” and you
reject the null hypothesis.
• If the null hypothesis is true, the probability of
randomly getting the observed sample is unlikely.
• This provides evidence against the null
hypothesis and we would REJECT the null
hypothesis, suggesting one of the alternative
hypotheses were correct.
Statistical Significance
O If P value > 0.05,
O You say the results were “not statically
significant”
O If the null hypothesis is true, the probability
of randomly getting the observed sample is
likely.
O This does not provides evidence against the
null hypothesis and we would FAIL TO
REJECT the null hypothesis, allowing us to
reject the alternative hypotheses.
Statistical Tests/Hypothesis
Testing/Inferential Test:
O All statistical tests provide a P value that is the
probability that your results would have occurred if
the null hypothesis were true.
Statistical Tests/Hypothesis
Testing/Inferential Test:
O All statistical tests provide a P value that is the
probability that your results would have occurred if
the null hypothesis were true.
O They use information from your data (mean, standard
deviation, etc.) to figure out a probability based upon
a population that meets the null hypothesis (much
like coin simulation).
Statistical Tests/Hypothesis
Testing/Inferential Test:
O All statistical tests provide a P value that is the
probability that your results would have occurred if
the null hypothesis were true.
O They use information from your data (mean, standard
deviation, etc.) to figure out a probability based upon
a population that meets the null hypothesis (much
like our card simulation).
O You use the p-value to make a data-driven decision
So what do you do with this
information?
O If the p-value says “fail to reject” the null
hypothesis, but you see a significant trend in
your raw data, more trials is the way to go,
especially if the trend is what you would
expect based on your background research.
What if the trend is not what
you expected?
O If the trend in your data is not what you
would expect based on your background
research, then you need to examine the
science further (more background research).
Examining the science
O Here are some ideas to consider:
O pH: all living tissue has BUFFERS which resist
changes in pH up to a certain point; enzymes begin
to denature at certain pH values
O Temp: enzymes begin to denature at certain
temperatures.
O Enzyme/substrate concentration: perhaps you do
need to consider the “freshness” of your sample as
well as the starting concentration before you
doubled or diluted it.
Flaws in your technique
O Yes, of course you are not a perfect person
and you are also quite inexperienced in
working in a lab, so there is lots of room for
improvement here, BUT…
O If the methodology is “tried and true” (which
for all of you it was), then the better way to
improve your results is to dig deeper into the
science, in addition to practicing those skills
and being more consistent in your
techniques.
Nuts and Bolts
O Proof read your work!!! Please! Out loud!
O Do not Capitalize Words that Are Not Proper
Nouns unless they begin a sentence!
O Format your data tables and graphs to fit on
the page completely. There’s no magic
button, just a lot of trial and error to make it
look right!
O Do not waste paper. Double space, and
remove extra space between sections.
Next Steps…
O Use this information to revise your paper.
O Ask questions in Titan Time or before/after
school.