Constructing Hypotheses

7/28/2019 Constructing Hypotheses

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ISPS :

CONSTRUCTINGHYPOTHESES

KPLI & KDPM

LECTURE NOTES


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MR. SYLVESTER SAIMON SIMIN, MPKS3

STEPS FOR WRITING HYPOTHESIS

1. Identify variables in a given event orrelationship.

2. Identify a pair of variables that might be

logically related.3. Identify the manipulated and responding

variables.

4. Write the hypothesis using the format: If the (MV) increases / decreases, then the

(RV) will increase / decrease


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EXAMPLE 1

PROBLEM / QUESTION

Rosli raises bees. He noticed that differentnumbers of young hatched from the samenumber of hives at different times. Hewondered what factors might influence thehatching rate of bees. He selected thefollowing variables to be tested:

1. Temperature of the hive

2. Relative humidity inside the hive

3.Amount of food available

4. Number of bees living in the hive.

Construct a hypothesis for each variable listedabove.


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ANSWER FOR EXAMPLE 1

1. As the temperature of hive increases, thehatching rate will increase.

2. As the relative humidity inside the hive

increases, the hatching rate will decrease.

3. As the amount of food available decreases,

the hatching rate increases.

4. As the number of bees living in the hive

increases, the hatching rate decreases.


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EXAMPLE 2

PROBLEM / QUESTIONWhat factors determine the rate

at which an object falls through

air?

List 4 possible variables and

construct a hypothesis for eachvariable.
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ANSWER FOR EXAMPLE 2Possible variables:

a. Volume of objectb. Surface area of object

c. Length of fall

d. Weight of object

Hypothesis:

Volume of objectAs the volume of an object increases, the rate at which it fallsthrough air decreases.

Surface area of object

As the surface area of an object increases, the rate at which itfalls through air decreases.

Length of fallThe longer or farther an object falls through air, the faster it willfall

Weight of object

The more weight and object has, the faster it will fall through air



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ITS YOUR TURN (EXERCISE 1)

PROBLEM / QUESTIONWhy is it warmer in one house

than another?


construct a hypothesis for

each variable.
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SAMPLE ANSWER EXERCISE 1

Outside temperature The higher the outside temperature, the higher the temperature

inside the house.

Location of house The nearer the house is to the equator, the higher the

temperature inside the house.

Slope of roof The steeper the roof, the higher the temperature inside the

house.

Thickness of insulation

The thicker the insulation, the higher the temperature inside thehouse.

Number of openings to the outside The more openings (windows and doors) to the outside, the

lower the temperature inside the house.




PROBLEM / QUESTIONWhat factors determine the

length of a shadow?


construct a hypothesis for

each variable.
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Height of object The taller the object, the longer its shadow.

Time of day

The closer the time moves toward noon, theshorter the shadow of an object.

Season of year

As the season progresses from summer towinter, the length of a shadow becomes

longer.




PROBLEM / QUESTIONWhat factors determine the

number of fleas on two

types of dog, a goldenretriever and a dachshund?

List 3 possible variables andconstruct a hypothesis for

each variable.
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Size of dog If dogs are larger, then they will have a larger

flea population than smaller dogs.

Length of hair If dogs have longer hair, then they will have

more fleas than dogs with shorter hair.

Presence of flea collar

If dogs have flea collars, then they will have

fewer fleas than dogs without flea collars.



EXERCISE 4

Which of the following are stated as hypotheses?1.As more salt is dissolved in water, the water willbecome cloudy.

2. The earths crust contains 90 elements.

3. Magnetism and gravity are not the same.4. If the length of a vibrating string is increased,

the sound will become louder.

1, 4Remember, a hypothesis is stated as the predicted effectone variable (MV) will have on another (RV)



EXERCISE 6

Which of these statements are hypotheses?

1. As the temperature of its environment increases, the

temperature of a cold-blooded animal increases.

2. Glass is harder than iron; therefore glass will

scratch anything which is softer than iron.3. A change in weather causes a change in mood

1, 2, 3

In all three cases we are predicting what will happen to aresponding variable if we manipulate another variable.



EXERCISE 7Which of these statements are hypotheses?

1. If clouds act as insulators, then the earth should get

colder on cloudless nights.

2. Leaves manufacture food, stems transfer food, and

roots store the food in plants.

3. The colder the temperature, the slower plants grow.

4. The deeper one dives, the greater the pressure.

5. Algae are living organisms.

1, 3, 4



EXERCISE 8

Read the description of investigations in thefollowing slides. Then, answer the

following questions.

1. What are some of the constants?2. What variable was manipulated?

3. Which variable was expected to respond?

4. What was the hypothesis being tested?



EXERCISE 8 INVESTIGATION 1

John was interested in determining the effect thenumber of plants located in an area has on growth

rate. He planted radish seeds in several milk

cartons. In the first carton, he planted 5 seeds 1

cm deep and no less than 5 cm apart; in thesecond, 10 seeds were planted 1 cm deep and no

more than 2 cm apart; in the third, 15 seeds, 1 cm

deep and 1 cm apart; and in the fourth, 20 seed, 1

cm deep and 0.5 cm apart. Each carton waswatered daily and daily measurements of the

length of leaves were made.



ANSWER FOR EXERCISE 8

INVESTIGATION 11. Factors that were kept the same:

Kind of seed, planting depth, type of soil,environmental temperature, amount of water, kindof containers, and amount of light received.

2. Manipulated variable : number of plants in an

area3. Responding variable : Growth rate (OD =

length of leaves)

4. As the number of plants in an area increases,

the length of the leaves will become shorter.OR

As the number of plants in an area increases,the length of the leaves will become longer



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EXERCISE 8 EXPERIMENT 2

Is there a relationship between the amount oftraining received and the length of time alearned behaviour persists in insects? Selecta number of sowbugs which always turn rightwhen entering the intersection of a T-shapedmaze. Using the tendency of sowbugs toavoid light, it is possible to train them to turnleft by shining a strong-light from the right asthey enter the intersection. Subject an animal

to 1, 5, 10, 15, or 20 training sessions. Testeach animal once an hour by running itthrough the T-maze.



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ANSWER FOR EXERCISE 8

EXPERIMENT 2

1. The constants: type of animal, shape ofmaze, strength of light source,

environmental temperature

2. MV : the amount of training3. RV : the length of time a learned

behaviour persisted

4. If the amount of training is increased,then the length of time a learned

behavior persisted will also increase.



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A TEACHERS REFLECTION

.The most common problem is that studentswrite a simple statement that is a cause and effectrelationship that makes a prediction (example: "If Ieat chocolate, then I will get pimples."). They haveto be reminded that what makes a hypotheticalstatement is the idea that two things might be, butnot necessarily related. In other words they failedto state a proposed relationship before making theprediction. Literally speaking, cause and effect

statements are based on unstated assumptions. Inmodels for scientific research, minimizingassumptions first and then stating your hypothesisis how variables are controlled.


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Constructing Hypotheses

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