Study guide

Complete LIFESCI 2A03 Notes

145 views 2 purchases

Course
LIFESCI 2A03 (LIFESCI2A03)

Institution
McMaster University (mcmasteru)

Complete LIFESCI 2A03 notes including all relevant lecture annotations, in-depth figure analysis, and step-by-step explanation of difficult concepts. Received an A in the course.

[Show more]

Preview 3 out of 28 pages

View example

Uploaded on August 21, 2020
Number of pages 28
Written in 2019/2020
Type Study guide

CA$22.43

Added

Add to cart Add to wishlist

100% satisfaction guarantee
Immediately available after payment
Both online and in PDF
No strings attached

Scientific Method: Lecture 1

Characteristics of Science
• Based on empirical knowledge
◦ knowledge derived from observation or experimentation
‣ data collection (quantitative or qualitative)
◦ observations - often the starting point of a scientific investigation
• Provides rational/natural explanations
◦ seeking explanations in terms of rational/natural causes
◦ very few questions are off-limits in science - but the answers science can provide are limited to
the natural world
• Repeatable and reproducible (and reliable)
◦ scientific results are always subject to confirmation by the same or other investigators
‣ makes the study more reliable/powerful
◦ if experiments can be repeated/reproduced via a reliable method/procedure -> confirmation ->
reliable findings
◦ sometimes due to impracticality, temporal difficulties, or expense, it's not possible to repeat/
reproduce experiments
• Testable
◦ a good theory isn't enough - must be testable via experiments
◦ for an idea to be testable, it must generate specific expectations
‣ a set of observations/results are expected if idea true
‣ same expected if false
◦ sometimes to test ideas, the development of new tools may be required
• Involves experimentation
◦ an organized and detailed series of steps to validate or reject a hypothesis
• Generality of principles
◦ science seeks generality of principles
‣ generality is the establishment of universal principles that express how the natural world
works under certain conditions

The Scientific Method
1. define/identify a problem/question (usually arises from observation)
2. formulate a hypothesis (a potential explanation)
3. test the hypothesis - make observations or perform experiments and collect data
4. analyze data/results
5. does the data support the hypothesis? - if no, make new hypothesis/experiments
6. draw conclusions
7. communicate results

Case Study: Human Chromosome Count
• in 1923, Theophilus Painter reported that there were 48 chromosomes in a human cell
◦ had serial sections of testicular cells in metaphase and chromosomes were clumped together
and curled in
• this number was believed and accepted for 33 years - scientists used the same technique he used to
experiment

,• in 1950's new techniques were used such as hypotonic treatment, treatment with colchicine and
ideograms to count chromosomes
◦ 1952 - Tijo and Levan reported 46 chromosomes
• so what was wrong with Painter's approach? - he was only working with samples from a single patient
◦ we don't know if he had any chromosome aberrations
◦ single chromosome could have been counted as 2
• people often see what they expect/want to see - this is bias

Scientific Method: Lecture 2

Reasoning

Inductive Deductive
• inductive: summarizes a set of observations and
serves to provide predictions about unseen
events
◦ Ex. this ice is cold, therefore ALL ice is cold
• deductive: going beyond formulation of
hypotheses formed by induction & test if correct
◦ Ex. if all green apples are sour, then this
green apple will be sour

The Hypothesis
• statement or idea proposed as tentative explanation to a research question and the account for
observations
◦ question -> hypothesis -> prediction -> experiment
• should be:
◦ simple
◦ specific
◦ stated in advance
• it leads to predictions about the result of intervention

Testing the Hypothesis
• the formulation and testing of hypothesis is the basis of any scientific or rational inquiry
• deductive syllogism: hypothesis followed by a prediction
◦ i.e. "If (hypothesis) ..., then (prediction)
• Ex. hypothesis: all swans are white
◦ prediction: swans that live in America should be white
◦ If all swans are white, American swans should also be white

Prediction and Hypothesis Testing
• predictions can be verified or refuted by analyzing the data
◦ accumulation of supporting experimental evidence (i.e. consistent with your prediction) will
strengthen a hypothesis but will never let us know for certain that the hypothesis is true
‣ therefore, you fail to reject the hypothesis
◦ a contradictory observation to your prediction (i.e. if the results you obtain are inconsistent

, with your prediction) allow us to know for (almost) certain that a hypothesis is incorrect
‣ therefore you reject the hypothesis

Null vs Alternative Hypothesis
• Null hypothesis (H0): usually a statement of 'no effect' or 'no difference'
◦ a hypothesis that there is no significant different between two sets of results, e.g.:
‣ between observations from a control group and experimental group
‣ between observations of two groups in two different conditions
‣ between a set of predicted results and the observed results
• Alternative hypothesis (Ha): hypothesis that is contrary to the null hypothesis
◦ usually the research hypothesis
◦ this is the hypothesis that you are trying to
'prove'
• as seen in the table, a type I error is one in which the BoB
null hypothesis is rejected, but in reality we should
have failed to reject
• a type II error is one in which we fail to reject the null
when we should have rejected it

Case Study: Brain Freeze
• Ha: the rate at which you eat ice cream affects whether you will experience an ice cream headache
• Ho: there is no effect of the rate of eating ice cream on the incidence of ice cream headaches
◦ i.e. there is no statistical difference in either observed effects (they both either cause headaches
or they don't)
• The experiment: 145 middle school students were randomly placed into 2 groups:
◦ Eat slowly group: eat ice cream in over 30 seconds (100mL)
◦ Eat fast group: eat it in 5 seconds (100mL)
• Results: found that in slow group, 9% had headaches whereas fast group 27% has headaches
◦ a chi-square test can be done to see if these values are statistically significant
• Drawing conclusions:
◦ if researchers rejected the Ho: data supports Ha or is consistent with the Ha
◦ if failed to rejected the Ho: they didn't detect a difference between groups and there is no
evidence to support Ha
‣ this basically means they accepted the null hypothesis

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller dhanotas. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for CA$22.43. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

75323 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling