The Scientific Method

Classical ApproachDr. M. Hazlett

MHS

The Classical Scientific Method(or how everyone wants you to think

science really works. . . .)

The Scientific Method consists of several steps – but at times they are or can not be done in the proper order until the work is done!

But – let’s humor everyone and do them in order.

Step 1:• Observation

– In this step a problem or question about how or why something does what is does, or what happened, or what happens if A is added to B, or why is something the way it is, etc. is asked

– Obviously – you want to discover something or simply answer a nagging question

• For example – why don’t we see baby pigeons?• Or – should you shave your body during an

earthquake?

Step 2:• Research the Question

– This is called developing a literature review– Nowadays – the internet has made this step so much

easier – but beware of the misinformation out there• You must rely on reputable sources – in peer refereed

journals or publishers.• Check the footnotes and bibliographies for more sources and

possible leads.• A good rule of thumb for when to stop researching is when

the information starts repeating itself and you’re not finding anything new. This means there is no set limit on the number of sources.

Step 3:• Develop Hypotheses

– This means creating a testable question– If you can’t test it – it is not a hypothesis– In the hypothesis – you have variables

• These are the concepts representing the cause and effect; or two or more things that are related, etc.

– The Causal Variable is called the Independent Variable (IV) or the Manipulative Variable

– The Effect Variable is called the Dependent Variable (DV)

In other words . . . .• Independent Variable (IV) is the cause –

usually what you are trying to figure out– For example: What causes a certain disease? The

cause is the IV– The disease (or the effect) is the dependent variable

(DV) – The DV is typically set and does not change in the

experiment. If it does, then you may have another variable interfering in your hypothesis that you didn’t count on

• You should control for these up front!

Step 4:Experimentation or Testing

In this step you actually perform the experiment.

It is extremely important that you use the proper equipment and carefully record each and every step, attempt or whatever that you do to test your hypothesis.

In doing this, you are preserving two concepts - VALIDITY and RELIABILITY

Validity and Reliability• The idea behind reliability is that any significant results

must be more than a one-off finding and be inherently repeatable.

• Other researchers must be able to perform exactly the same experiment, under the same conditions and generate the same results. This will reinforce the findings and ensure that the wider scientific community will accept the hypothesis.

• Without this replication of statistically significant results, the experiment and research have not fulfilled all of the requirements of testability.

• This prerequisite is essential to a hypothesis establishing itself as an accepted scientific truth.

• For example, if you are performing a time critical experiment, you will be using some type of stopwatch. Generally, it is reasonable to assume that the instruments are reliable and will keep true and accurate time. However, diligent scientists take measurements many times, to minimize the chances of malfunction and maintain validity and reliability.

• At the other extreme, any experiment that uses human judgment is always going to come under question.

• Human judgment can vary wildly between observers, and the same individual may rate things differently depending upon time of day and current mood. Therefore, we rely on objective rather than subjective measures.

• Subjective means a researcher is measuring opinions or views – this is alright as long as the researcher remains consistent in the measuring and avoids personal biases.

• Physics and Chemistry are objective – the measures are the same around the world, no interpretations needed!

• Reliability is a necessary ingredient for determining the overall validity of a scientific experiment and enhancing the strength of the results.

• This is why we use carefully calibrated equipment.

Reliability• In normal language, we use the word reliable to mean that something is dependable

and that it will give the same outcome every time. We might talk of a football player as reliable, meaning that he gives a good performance game after game.

• Reliability is something that every scientist, especially in social sciences and biology, must be aware of.

• In the physical sciences, the definition is the same, but needs a much narrower and unequivocal and accepted definition.

• Another way of looking at this is as maximizing the inherent repeatability or consistency in an experiment. For maintaining reliability internally, a researcher will use as many repeat sample groups as possible, to reduce the chance of an abnormal sample group skewing the results.

• If you use three replicate samples for each manipulation, and one generates completely different results from the others, then there may be something wrong with the experiment.

• For many experiments, results follow a ‘normal distribution’ and there is always a chance that your sample group produces results lying at one of the extremes. Using multiple sample groups will smooth out these extremes and generate a more accurate spread of results.

• If your results continue to be wildly different, then there is likely to be something very wrong with your design; it is unreliable.

Reliability Example – Cold Fusion

• Reliability is also extremely important externally, and another researcher should be able to perform exactly the same experiment, with similar equipment, under similar conditions, and achieve exactly the same results. If they cannot, then the design is unreliable.

• A good example of a failure to apply the definition of reliability correctly is provided by the cold fusion case, of 1989

• Two scientists announced to the world that they had managed to generate heat at normal temperatures, instead of the huge and expensive equipment used in most research into nuclear fusion.

• This announcement shook the world, but researchers in many other institutions across the world attempted to replicate the experiment, with no success. Whether the researchers lied, or genuinely made a mistake is unclear, but their results were clearly unreliable even if the experiment was valid in the first place.

• Reliability is an essential component of validity but, on its own, is not a sufficient measure of validity. A test can be reliable but not valid, whereas a test cannot be valid yet unreliable.

• Reliability, in simple terms, describes the repeatability and consistency of a test. Validity defines the strength of the final results and whether they can be regarded as accurately describing the real world.

Citation: Shuttleworth, Martyn (2009). Definition of Reliability. Retrieved [10 July 2011] from Experiment Resources: http://www.experiment-resources.com/Definition-of-reliability.html

Step 5: Data Analysis• After carefully collecting all of the data and recording it, it is time to

analyze it.• Often, results must be converted from the American system of

measurement to the SI or metric system.• If you mess this up – it can be very expensive • For example – a mistake in converting measurements in the Hubble

Telescope required a Space Shuttle trip to repair it!

Conversions

You have to be able to do this! A study guide is on my website – print it out! There are some basic measures and units you should know and the sooner you do, the easier the class.

This is because the U.S. is one of only two nations in the world that does not solely use the metric system! In the physical sciences – we only use SI!

1. Temperature Scales and Conversions

Celsius / Centigrade Fahrenheit Kelvin

•Water Freezes 0 o 32o 273.16o

•Water Boils 100o 212o 373.16o

 

•Temp Celsius (Tc) Tc = (5/9) x (Tf – 32) or (0.56) x (Tf – 32)

•Temp Fahrenheit (Tf) Tf = (9/5 x Tc) + 32 or (1.8 x Tc) + 32

•Temp Kelvin (Tk) Tk = Tc + 273.16

•Temp Rankine (TR) TR = Tf + 460

The Metric System

SI Prefixes – LEARN THESE!

These prefixes will be followed by meter or gram. 

•1012 = tera (T) 1 000 000 000 000

•109 = giga (G) 1 000 000 000

•106 = mega (M) 1 000 000

•103 = kilo (k) 1 000

•102 = hecto (h) 100

•101 = deka (da) 10

•10-1 = deci (d) 0.1

•10-2 = centi (c) 0.01

•10-3 = milli (m) 0.001

•10-6 = micro () 0.000 001

•10-9 = nano (n) 0.000 000 001

•10-12 = pico (p) 0.000 000 000 001

•10-15 = femto (f) 0.000 000 000 000 001

Some common conversions – knowing these will make your life easier!

• 1 mile = 1760 yards = 5280 ft• 1 yard = 3 feet = 36 inches• 1 gallon = 4 qts = 8 pts = 16 cups = 128 oz• 1 inch = 2.54 cm• 10 mm = 1 cm; 100 cm = 1 m; 1000 m = 1 km• 1000 mL = 1 L• 1000 g = 1 kg

• Other equivalencies are on the front wall and in the study guide on my webpage!

How to convert between American and SI

• Dimensional Analysis (also called Factor-Label Method or the Unit Factor Method) is a problem-solving method that uses the fact that any number or expression can be multiplied by one without changing its value. It is a useful technique. The only danger is that you may end up thinking that science is simply a math problem - which it definitely is not, but a lot of it is! Sorry!

• Unit factors may be made from any two terms that describe the same or equivalent "amounts" of what we are interested in. For example, we know that

• 1 inch = 2.54 centimeters

• Note: Unlike most American-Metric conversions, this one is exact. There are exactly 2.540000000... centimeters in 1 inch.

• We can make two unit factors from this information:

• Now, we can solve some problems. Set up each problem by writing down what you need to find with a question mark. Then set it equal to the information that you are given. The problem is solved by multiplying the given data and its units by the appropriate unit factors so that only the desired units are present at the end.

• For example: You want meters, and are given the data in inches. So –

Given Unit (inches) x Wanted Unit (meters)

Equal Amount in Given

Units (# inches in a meter)

The inches cancel-out leaving your answer in meters

• Example:– Note the fraction you multiply by is equal to

one. (1 inch = 2.54 cm)

= You use an one/one fraction each time regardless of what the conversion is!

= This is why learning the basic equivalences will make life easier

• More examples: How many seconds in two years?

• What is the density (D) of mercury (13.6 g/cm3) in units of kg/m3?

Scientific Notation (Powers)

• We will always be using scientific notation and rounding off to three decimal places

• Scientific Notation means it will be a number times ten to a certain power; example 3.4 x 104

• If the power is positive, this means you would be moving the decimal to the RIGHT the proper number of spaces – so 3.4 x 104 is equal to 34000 – or if you wanted to write 34000 in scientific notation, move the decimal to the LEFT four spaces. (One whole number needs to be on the left of the decimal)

• If it is 5.1 x 10-2, this is the same as 0.051 – the decimal was moved to the RIGHT to make it into scientific notation

• Your calculator will give numbers like 5.6E12. This is the same as 5.6 x 1012

• DO NOT WRITE ANSWERS USING THE “E”, USE THE “x 10Power” IN YOUR ANSWERS

• If multiplying two numbers with scientific notation, multiply the numbers and then add the powers together– Ex.: (5 x 103)(3 x 102) = (5 x 3) x 103+2

= 15 x 105

• When dividing numbers with scientific notation, divide the numbers and then subtract the powers

• Ex.: (10 x 1023) / (2 x 1015) =

(10/2) x 1023-15 =

5 x 108

P.S. Make sure your calculators are set for degrees and not radians or you may get

some weird answers doing the problems in these classes!

Step 6: Interpreting the Data• In this step, you use the data you have collected

to determine whether or not your hypothesis is supported

• Again – remember to maintain the validity and reliability in your analysis

Here is an ongoing experiment. This close-up image shows the 'Materials on International Space Station Experiment-8.' Taken during the spacewalk on July 12, 2011, the small circles pictured are test beds for materials and computing elements attached to the outside of the International Space Station. These elements are being evaluated for the effects of atomic oxygen, ultraviolet, direct sunlight, radiation, and the extremes of heat and cold. Researchers hope the results will provide a better understanding of the durability of various materials and computing elements when they are exposed to the rigors of space environments and hope to incorporate what is learned into the design of future spacecraft. Image Credit: NASA, 7/14/11

Step 7: Communicating your Results

• This just may be the most important step of them all• You have to be able to accurately and clearly express

your research and findings• Remember your intended audience – you would explain

the same things differently for school children or a group of doctors

So, the scientific method may be better typified by this diagram with its interconnected steps surrounding a single, well defined research question.

Finally, in conclusion:• Look or make a copy of the Scientific Measurement Study Guide –

it’s the same one for Physics, Chemistry and Physical Science• Learn the more common conversions – some are up on the wall at

the front of the class – but they will not always be there!• Practice the converting process by doing the worksheets and

turning them in on time – don’t be lazy! Each counts as a grade!

• Finally – DO NOT PANIC!!

ASK FOR HELP!!