Back to homeLife Sciences · Secondary Year 2 · Change subject
Start for free
Secondary 2 · Life Sciences
Scientific Activity · The scientific method

Observing and Analyzing Data

A thermometer reads "36." Is that 36 degrees Celsius, 36 Fahrenheit, or the temperature of an animal with a fever? Without units and context, a piece of data is useless. That is why it matters so much how data are collected, organized, and presented in science.

Data Tables

During recess you count the pigeons in the school courtyard and jot it down on a scrap of paper: Monday 12, Tuesday 9, Wednesday 15... If you have dozens of loose observations, how do you organize them so you can look them up and compare them at a glance?

Data table with two columns titled "Pigeons seen in the courtyard," showing the day of the week and the number of pigeons observed. Pigeons seen in the courtyard Day No. of pigeons Monday12 Tuesday9

It is also important to know what is being measured and with what. If you are studying how a plant grows, the quantity is height, the instrument is a ruler or measuring tape, and the unit is the centimeter (cm). Choosing the quantity, the instrument, and the unit well is part of collecting good data.

Practice★☆☆Not started
You have counted the pigeons seen in the playground over five days: 12, 9, 15, 11, and 14. Draw a properly made data table, with a title and column headings, to record…

You have counted the pigeons seen in the playground over five days: 12, 9, 15, 11, and 14. Draw a properly made data table, with a title and column headings, to record those values.

You can do it on paper and send a photo with your answer.

Solve
Practice★☆☆Not started
A table reads: "the school sports court measures 100". Explain what information is missing for the data to be complete and why units are essential in a table of…

A table reads: "the school sports court measures 100". Explain what information is missing for the data to be complete and why units are essential in a table of scientific data.

Solve
Practice★☆☆Not started
To study how a plant grows we measure its height every week. State which quantity we are measuring, which instrument you would measure it with, and in which unit you…

To study how a plant grows we measure its height every week. State which quantity we are measuring, which instrument you would measure it with, and in which unit you would express the data.

Solve
Practice★★★Not started
You are going to investigate whether soil type (sand, clay, or garden soil) affects the growth of lentil plants over 15 days. Design the data table you would use to…

You are going to investigate whether soil type (sand, clay, or garden soil) affects the growth of lentil plants over 15 days. Design the data table you would use to collect the results: state what columns and rows it would have and what units you would use.

Solve

Qualitative and Quantitative Data

When you examine a rock in the lab, you write down: "it is gray with shiny specks, rough in texture, and weighs 240 g." What is the difference between observations stated in words and those measured with a number?

Comparison of quantitative and qualitative data: on the left, a 5 cm leaf is measured with a ruler and 14 bees are counted; on the right, yellow flowers are described in words. Quantitative 5 cm 0 1 2 3 4 5 cm 14 bees Qualitative yellow flowers
Practice★☆☆Not started
Explain the difference between qualitative data and quantitative data, and classify these observations from the playground: "the flowers are yellow", "there are 14…

Explain the difference between qualitative data and quantitative data, and classify these observations from the playground: "the flowers are yellow", "there are 14 bees", "the leaves are $5\ \text{cm}$ long", and "the air smells of wet grass".

Solve

Calculating and Interpreting: The Mean

Three classmates measure the same leaf and get 8.1 cm, 8.3 cm, and 8.2 cm. Which one do you go with? When we repeat a measurement, the results are similar but not identical. To summarize them we use the mean.

Watch out for precision: if repeated measurements are very close to one another (8.1, 8.3, 8.2), the measurement is precise. If they are widely scattered (7.5, 9.0, 8.1), it is not very precise.

Practice★★☆Not started
The maximum temperatures one week were 20, 22, 23, 25, 24, 26, and 21 degrees Celsius. Calculate the mean temperature for the week and point out which two days were…

The maximum temperatures one week were 20, 22, 23, 25, 24, 26, and 21 degrees Celsius. Calculate the mean temperature for the week and point out which two days were furthest from that mean.

Solve
Practice★★☆Not started
Two groups measure the length of the same leaf three times. Group A gets $8.1\ \text{cm}$, $8.3\ \text{cm}$, and $8.2\ \text{cm}$; Group B gets $7.5\ \text{cm}$,…

Two groups measure the length of the same leaf three times. Group A gets $8.1\ \text{cm}$, $8.3\ \text{cm}$, and $8.2\ \text{cm}$; Group B gets $7.5\ \text{cm}$, $9.0\ \text{cm}$, and $8.1\ \text{cm}$. Calculate the mean for each group and determine which of the two measured with greater precision.

Solve
Practice★★☆Not started
Five classmates measure their resting heart rates and get 72, 80, 68, 76, and 74 beats per minute; after running for two minutes they get 108, 116, 102, 110, and 104.…

Five classmates measure their resting heart rates and get 72, 80, 68, 76, and 74 beats per minute; after running for two minutes they get 108, 116, 102, 110, and 104. Calculate the mean in each situation and write a two-line conclusion.

Solve
Practice★★☆Not started
A bean plant, which sprouts at the start of the first week with a height of 0 cm, is 2 cm tall at the end of the first week, 6 cm at the end of the second, 11 cm at the…

A bean plant, which sprouts at the start of the first week with a height of 0 cm, is 2 cm tall at the end of the first week, 6 cm at the end of the second, 11 cm at the end of the third, and 17 cm at the end of the fourth. Calculate how much it has grown in total and its mean weekly growth, and determine whether it has grown at the same rate every week.

Solve
Practice★★★Not started
The marks of two groups of five students are: group A, 2, 5, 6, 7, and 10; group B, 6, 6, 6, 6, and 6. Calculate the mean of each group and explain why, although the…

The marks of two groups of five students are: group A, 2, 5, 6, 7, and 10; group B, 6, 6, 6, 6, and 6. Calculate the mean of each group and explain why, although the means are the same, the two groups are not alike; explain what information is lost when only the mean is given.

Solve
Practice★★★Not started
When measuring the time it takes for a leaf to fall from $2\ \text{m}$, the following values in seconds are obtained: 3.1, 2.9, 3.0, 7.8, 3.2. One of them is clearly…

When measuring the time it takes for a leaf to fall from $2\ \text{m}$, the following values in seconds are obtained: 3.1, 2.9, 3.0, 7.8, 3.2. One of them is clearly anomalous. Identify it, suggest a possible cause for this error, and decide, with reasoning, what to do with this data point when calculating the mean.

Solve

Choosing the Type of Graph

You have the temperature recorded every hour during a hike up Pico Duarte and the number of trees of each species you found. How do you turn those lists into a picture that can be understood at a glance?

Schematic comparison of three graphs: line graph for change over time, bar graph for comparing categories, and pie chart for parts of a total. lines: change over time bars: compare categories circular: parts of a total

In a graph, the variable you control, or time, goes on the horizontal axis (x), and the variable being measured goes on the vertical axis (y). Each axis has its name and unit, and the graph has a title.

Practice★☆☆Not started
You want to represent three sets of data: (a) how classroom temperature changes throughout the day, (b) the percentage of students choosing each sport, and (c) the…

You want to represent three sets of data: (a) how classroom temperature changes throughout the day, (b) the percentage of students choosing each sport, and (c) the number of different species observed in each area of the playground. State which type of graph (line graph, circle graph, or bar graph) you would choose in each case and justify your choice.

Solve
Practice★☆☆Not started
The graph shows the height reached by some plants depending on the hours of light they receive each day. Describe the relationship between both variables and, using the…

The graph shows the height reached by some plants depending on the hours of light they receive each day. Describe the relationship between both variables and, using the grid lines to help you, estimate the approximate height of a plant receiving 6 hours of light per day.

2 4 6 8 10 5 10 15 20 25 hours of light per day height (cm) ?
Solve
Practice★☆☆Not started
The temperature of a glass of hot water cooling on a table is measured: at 0 min it reads $60\ ^\circ\text{C}$, at 5 min $52\ ^\circ\text{C}$, at 10 min…

The temperature of a glass of hot water cooling on a table is measured: at 0 min it reads $60\ ^\circ\text{C}$, at 5 min $52\ ^\circ\text{C}$, at 10 min $45\ ^\circ\text{C}$, at 15 min $40\ ^\circ\text{C}$, and at 20 min $36\ ^\circ\text{C}$. What was the temperature at 10 minutes? In which time interval did the temperature drop the fastest?

Solve
Practice★☆☆Not started
In a bar chart about animals seen in the park, the bars show: sparrows 8, pigeons 5, blackbirds 2, and squirrels 1. Which animal was observed most often? How many…

In a bar chart about animals seen in the park, the bars show: sparrows 8, pigeons 5, blackbirds 2, and squirrels 1. Which animal was observed most often? How many animals were counted in total? What title would you give the chart?

Solve
Practice★★☆Not started
You are going to plot on a line graph how the depth of a puddle changes over ten days of drought. Explain which variable you will place on each axis, which units you…

You are going to plot on a line graph how the depth of a puddle changes over ten days of drought. Explain which variable you will place on each axis, which units you will use, and why time is almost always plotted on the horizontal axis.

Solve

Graphs That Inform... or Mislead

A newspaper says, "Library A gets far more visits than Library B!" and shows two bars of very different heights. Is it true, or is there a trick?

A well-made graph has a title, axes labeled with units, and says how many data points it represents (for example, "30 students surveyed"). And the vertical axis of bar graphs must start at 0.

Another common mistake is confusing correlation with causation. Two variables can vary together without one causing the other: at Boca Chica beach, more ice cream is sold in the hot months and there are also more swimmers, but ice cream does not make people go to the beach. There is a common cause: the heat.

To show that A causes B, you need an experiment: change only A, keep everything else the same, and compare with a control group.

The sample also matters. If, to find out the school's favorite sport, you ask only the soccer team, the result does not represent everyone. A reliable sample is large and varied: for example, randomly choosing students from all grades and of both sexes.

Practice★★☆Not started
A bar chart about the class's favorite fruits has no title, no axis labels, and it is not known how many people were asked. Explain what problems this chart has when it…

A bar chart about the class's favorite fruits has no title, no axis labels, and it is not known how many people were asked. Explain what problems this chart has when it comes to being interpreted and which three things you would add.

Solve
Practice★★☆Not started
It is observed that the months with the highest ice cream sales are also the months with the most bathers on the beach. Does that mean eating ice cream causes people to…

It is observed that the months with the highest ice cream sales are also the months with the most bathers on the beach. Does that mean eating ice cream causes people to go to the beach? Explain the difference between correlation and causation using this example.

Solve
Practice★★☆Not started
To find out the favorite sport of the school's students, a group decides to ask only the members of the soccer team. Explain why this sample does not represent the whole…

To find out the favorite sport of the school's students, a group decides to ask only the members of the soccer team. Explain why this sample does not represent the whole school and describe how you would choose the sample so that the result was more reliable.

Solve
Practice★★★Not started
Two bar charts show the same data on visits to two libraries, but in one the vertical axis starts at 0 and in the other it starts at 950 visits, so the difference…

Two bar charts show the same data on visits to two libraries, but in one the vertical axis starts at 0 and in the other it starts at 950 visits, so the difference between the bars looks enormous. Explain which trick is being used, why it can mislead the reader, and what an honest chart should look like.

Solve
Practice★★★Not started
A study finds that students who spend more hours in the library get better marks, and a newspaper headline reads: "The library boosts marks". Give at least two…

A study finds that students who spend more hours in the library get better marks, and a newspaper headline reads: "The library boosts marks". Give at least two alternative explanations for this correlation and explain what type of experiment would be needed to state that a cause-and-effect relationship exists.

Solve

Fieldwork and Mini-Projects

To compare two areas of the courtyard (sun and shade), it is not enough to just look: you have to measure under the same conditions. That way the result depends on the area and not on how you counted.

In an experiment with groups (for example, soaked and unsoaked lentils), you compare using percentages: $\text{percentage} = \frac{\text{germinated}}{\text{total}} \times 100$. This way you can compare groups even if they are different sizes. And a single trial confirms nothing: it is repeated several times.

Practice★★★Not started
In a germination experiment, out of 10 lentils soaked in water, 8 germinated in three days, whereas out of 10 unsoaked lentils, 5 germinated. Organise the data into a…

In a germination experiment, out of 10 lentils soaked in water, 8 germinated in three days, whereas out of 10 unsoaked lentils, 5 germinated. Organise the data into a table, calculate the germination percentage of each condition, and write a three-line conclusion stating whether soaking seems to help and what you would do to confirm it.

Solve
Practice★★★Not started
You suspect there are more invertebrate species in the sunny area of the playground than in the shady area. Design the fieldwork: how you will make the counts so they…

You suspect there are more invertebrate species in the sunny area of the playground than in the shady area. Design the fieldwork: how you will make the counts so they are comparable (same time, same hours, same effort), which table you will use to collect the data, and which type of graph you would choose to compare both areas. State also how you will respect the animals.

Solve
Practice★★★Not started
Mini-project: measure the classroom temperature three times a day (first thing in the morning, at midday, and at the end of the school day) for a week. Before starting,…

Mini-project: measure the classroom temperature three times a day (first thing in the morning, at midday, and at the end of the school day) for a week. Before starting, predict the shape the line graph will have; then organise the data into a table, draw the graph, and comment on two factors that may have altered the values (the heating, open windows, the number of people).

You can do it on paper and send a photo with your answer.

Solve

Back to the beginning: that "36" only makes sense with its unit: $36\ ^\circ\text{C}$ is a normal body temperature, while $36\ ^\circ\text{F}$ is equivalent to just $2.2\ ^\circ\text{C}$, almost like the inside of a refrigerator.

Summary

See all the exercises in this section