• explain phenomena (i.e how and why things happen)
• solve problems using evidence.

Scientific evidence provides facts that help to answer a specific question and either support or disprove an idea or theory. Evidence is often based on data that has been collected through observations and measurements. To allow Scientists to reach conclusions, evidence must be...

• repeatable - other people should be able to repeat the process
• reproducible - other people should be able to reproduce the same results
• valid - it must be repeatable, reproducible and answer the question.

• data presentation
•  observations
• investigations
• measurements
• conclusions and evaluations

What is the cycle of an observation?

1. Observation made
2. Hypothesis formed (to explain the observation)
3. Experiment designed
4. Data collected
5. Hypothesis tested
6. Hypothesis supported or disproved or modified
7. If the hypothesis is to be modified, repeat steps 2-6

In order to explain a phenomenon, Scientists make an observation. They then develop a hypothesis from this observation. What is a hypothesis?

1. Independent variable - can be changed by the person carrying out the investigation. For example, the amount of water a plant receives.
2. Dependent variable - measured each time a change is made to the independent variable, to see if it also changes. For example, the growth of the plant (measured by recording the number of leaves).

Continuous variables...

... can take any numerical value (including decimals). They are usually measurements, e.g. temperature.

Categoric variables...

... are variables described by a label, usually a word, e.g. different breeds of dog or blood group.

Discrete variables...

... only take whole-number values. These are usually quantities, e.g. the number of shrimp in a stream.

Ordered variables...

... have relative values, e.g. 'small', 'medium' or 'large'.

What two things do investigations have to be?

PRECISE

(to form a valid conclusion)

and

ACCURATE

Explain the following:

1. Accuracy of instruments
2. Resolution or sensitivity of instruments

1. Accuracy of instruments - a measurement close to true value or how accurately the instrument has been calibrated.
2. Resolution or sensitivity of instruments - it is determined by the smallest change in value that the instrument can detect. he more sensitive the instrument is, the more precise the value.

What are the three errors in measurement?

1. Human error - losing concentration or making the same mistake repeatedly (basically people being stupid).
2. Systematic error - can result from repeatedly carrying out the process incorrectly, making the same mistake each time.
3. Random error - can result from carrying out a process incorrectly on odd occasions or by fluctuations in reading.

 The dependent variable when presenting data on a graph or chart goes on the vertical axis, whereas the independent variable when presenting data goes on the horizontal axis.

Conclusions should...

• describe patterns and relationships between variables
• take all data into account
•  make direct reference to the original hypothesis or prediction
•  try to explain results or observations by making reference to the hypothesis as appropriate.

An evaluation looks at the whole investigation. It should consider...

• the original purpose of the investigation
• the appropriateness of the methods and techniques used
• the reliability and validity of the data
• the validity of the conclusions