Measurement & Hypotheses
Measurement is at the core of science. Agreeing on how ideas and outcomes can be measured and evaluated is crucial to testing hypotheses with experiments.
Speaker Notes:
Measurements imply values that are not only orderable but the distance between the values can be measured (ordered).
Reading Assignment
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In addition to the parts of chapter 1 that describe hypothesis testing and other parts of the scientific method, read appendix A1 and learn the units of the metric system, if you do not already know them.
Speaker Notes:
Exponential notation is very important to be familiar with in this course.
Measurement and Hypotheses
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Observations made with senses (not authority of books or human institutions) are the ultimate source (=authority) of scientific knowledge.
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Causes are inferred when observations can be organized into repeated patterns. The process of generating cause(s) is called induction.
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A hypothesis is a statement proposing how something works.
Speaker Notes:
Agreeing on how to interpret/measure observations is an important part of making observations.
OBSERVATIONS
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Scientists believe there is a ‘real world’ accessible through senses by everyone.
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Measurement and counts are something all individuals can agree on. Most scientific observations involve measurement.
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Instruments are built to improve measurement range (super large and super small), accuracy and precision.
Speaker Notes:
While attributes like love and hate have changed little in thousands of years, technology developed through ideas and measurement has changed the way people live in each of the last few generations.
Statistics
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A value calculated from a set of multiple measurements is called a statistic.
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Common, simple statistics:
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Mean
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Median
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Variance
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Range (best expressed as a pair of values, the smallest and largest observations)
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Speaker Notes:
5, 6, 3, 5, 4, 4, 7, 3, 6, 8, 3, 2, 6, 4
TYPES of Observations
(of interest to ecologists)
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Measurement of fundamental attributes: distance, mass, temperature, time.
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Measurement of rates, e.g. change per unit time, or even per time squared.
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Measurement of complex attributes, such as energy = g∙m2∙sec-2.
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Abundance, counts of individuals, N.
Speaker Notes:
E = mc2 = gm2sec-2 Go over the exponential way of expressing units.
MEASUREMENT
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Humans have devised many different systems of measurement. Scientists need a universal and simple system. The metric system was adopted by scientists.
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The SI (metric) system is based on powers of ten separated by 3 (orders of magnitude). Word prefixes allow one to write a large range of measurements succinctly.
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en.wikipedia.org/wiki/SI_prefix
Speaker Notes:
Thousand fold
Distance (=length) Measurement
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The meter (m) is the basic unit of length and, therefore, area and volume.
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People are mostly 1.5 to 2.0 m tall.
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Single-cell organisms such as algae and protozoa usually are smaller than 1 mm (millimeter) and larger than 1 μm (micrometer).
Speaker Notes:
How many 10um cubes (size of a big human cell) could fit in 15cm cube (approximate size of a human brain)?
Area & Volume Measurement
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Area is measured in squared units of length, l2, volume in cubed units of length, l3 = l•l•l.
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The ‘hectare’ is the measurement used for large areas such as a farm field. One hectare is 10,000 or 104 square meters (m2).
Speaker Notes:
An NFL football field including the endzones is a little over ½ a hectare (0.5348)
Mass Measurement
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The basic unit of SI mass is the kilogram, kg.
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Your textbook weighs 3.4 kg.
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Your weight (units of force) would be different on the moon than it is on earth, but your mass is the same both places.
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The mass of carbon in CO2 in the earth’s atmosphere is 778 Petagrams (=778x1015 g)
Speaker Notes:
The concentration of carbon dioxide in the atmosphere is about 350 ppm.
Volume measurement
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Liquids ‘fill’ containers so that the air/liquid boundary is level (due to gravity). This property makes it easy to measure volume of a container.
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The basic unit of liquid volume is the liter, l. One liter is 1000 cm3.
Speaker Notes:
Most grapes are about 1 ml in volume.
Most grapes are about 1 ml in volume.
The milliliter is 1/1000 of a liter and is 1 cubic centimeter.
Concentration
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Different compounds can be mixed in a solution. In such situation we usually measure the concentration of the less abundant component in the more abundant component.
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Molarity
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Percent
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PPM = parts per million, 1 ppm =0.0001%
Speaker Notes:
You have or will learn about molarity in chemistry.
Time Measurement
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The year is between 365 and 366 days. Calendars attempt to keep each day, say 1 May, in the same position about the sun in every year.
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The ‘second’ is the SI unit of time.
Speaker Notes:
Have other cultures devised different systems?
Temperature Measurement
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Temperature is an especially interesting attribute. There is an ‘absolute zero’.
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The Kelvin (K) scale places zero there, about 273° C below the freezing point of water.
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We usually use the Celsius scale in which water freezes at 0° and boils at 100°.
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°C = (°F – 32)*5/9
Speaker Notes:
People normally express values as integers. If only whole numbers are used the Fahrenheit scale is ‘finer’.
Induction
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Observations are organized by the mind into patterns. Patterns are repeatable spatial or temporal organizations.
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The next element of the sequence: 2, 4, 8, 16, ? is 32, as each element is twice the previous one.
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Using and inferring PATTERN is a basic human attribute not just for scientists.
Speaker Notes:
Here is another sequence: 100, 95, 89, 82, 74, ?
Deduction
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Sets of hypotheses provide a framework of knowledge which may be called theory or conventional wisdom. From such frameworks, ideas or hypotheses are derived (= deduced) using reasoning, logic and inspiration.
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Deduction makes specific predictions using general rules (framework of knowledge).
Speaker Notes:
The idea of global warming is deduced from properties of solar radiation and properties of different molecules in the atmosphere.
HYPOTHESIS
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A hypothesis is a statement about what one believes to be true and that can be evaluated by new observations.
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A hypothesis (statement) can be useful even when it is replaced by a new hypothesis in the future (= proved at least not to have been complete).
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e.g., Linnaeus hypothesized that the most fundamental separation of living organisms was between plants and animals.
Speaker Notes:
Linnaeus made this division (used the idea) without explicitly stating it as a hypothesis.
Scientist now are more insistent that ideas be explicitly stated as hypotheses.
EXPERIMENTAL Design
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Experiments devise situations in which ideas or hypotheses may be evaluated by observations.
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Manipulated conditions, e.g. a new drug being evaluated, are called ‘treatments’.
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A good experiment has a ‘control’ which evaluates the ‘no special treatment’ outcome.
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The control for a new drug is called a ‘placebo’. A placebo creates the illusion that a drug is being taken when no drug is in the ‘pill’.
Speaker Notes:
Treatments are categorical groups.
Populations and Probabilities
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Treatments may change the probabilities of outcomes for members of a population. Both outcomes, cancer & no cancer, occur in the control and other treatments.
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Statistical analysis of outcomes tell whether or not the probabilities of specific outcomes differ according to treatments.
Speaker Notes:
Without a drug 5% of infected individuals die, with the drug 3% of the individuals die. That is a dru that would be called effective.
PROBLEM
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Express the following values in units of meters using exponential notation.
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A. 0.012 mm
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B. 567,000 km
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C. 0.00000098 m
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D. 5’ 9”
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Convert 50° F to Celsius.
Speaker Notes:
Hypothesis: If these problems are difficult for you, you are going to have to put in more than 6 hours a week studying to earn a C.
Vocabulary
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Celsius scale
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Control
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Conventional wisdom
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Experimental design
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Hypothesis
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Observation
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Mean
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Median
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Measurement
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Treatment (group)
Speaker Notes: