Variables in an experiment

Correct answer: C. Independent and dependent variables

Sand amount is changed and filtration time is measured. In exams distinguish the changed and measured variables.

Correct answer: D. Type of filtering cloth

Different cloth porosity may affect filtration time. In exams keep the filtering material the same.

Correct answer: A. Inverse relationship

When one variable increases while the other decreases the relationship is inverse. In exams identify the relationship from graph direction.

Correct answer: B. The independent variable is changed the dependent variable is measured and controlled variables are kept the same

In a fair experiment one independent variable is changed and the dependent variable is measured. In exams remember to control other factors.

Correct answer: B. An average can be calculated to reduce the effect of random variation

The governing experimental principle is repetition and reliability. Taking three measurements at each independent-variable level allows the researcher to calculate a mean and notice unusually high or low readings. Averaging reduces the influence of random variation, so option B is correct. Repetition does not control the independent variable, remove the dependent variable, or guarantee identical results; those claims make A, C, and D incorrect.

Correct answer: A. Zero percent, five percent, ten percent, fifteen percent

The governing concept is choosing clear levels of an independent variable. Salt concentration is quantitative, so its levels should be numerical, ordered, and expressed with a unit or percentage. Option A provides four directly comparable concentrations: 0%, 5%, 10%, and 15%. The other choices use temperature, unrelated descriptors, or subjective categories, so they do not represent salt-concentration levels and cannot support a clear comparison.

Correct answer: B. Fertilizer amount, dry mass, water amount

The governing concept is identifying experimental variables by their roles. The independent variable is what the researcher deliberately changes, so it is fertilizer amount. The dependent variable is what is measured in response, so it is plant dry mass. A controlled variable is kept constant; water amount is an appropriate example. Therefore, option B gives the correct order. The other options place these roles in the wrong sequence.

Correct answer: A. प्रतिक्रिया समय का प्रतिनिधि आश्रित चर

The distance travelled by the ruler is an observable measurement used to estimate the less-directly measured reaction time. Therefore, it acts as a proxy dependent variable: it changes in response to the person’s reaction. The release position and ruler should be kept constant. Option B describes a controlled factor, C is not the best classification, and D is a repeated trial rather than a variable.

Correct answer: A. सभी परीक्षणों में एक ही प्रकार की गेंद उपयोग करना

The type, material and construction of a ball can affect how much energy it returns during a bounce. Using a different ball introduces a confounding variable, so the same type of ball should be used in every trial. The drop height must remain the independent variable. Option B would remove the intended comparison, while C and D make the test less fair.

Correct answer: A. तापमान तभी स्वतंत्र चर होगा जब उसे जानबूझकर अलग-अलग स्तरों पर बदला जाए

An independent variable is the factor deliberately selected and changed by the investigator to study its effect. Merely naming room temperature does not make it independent. If temperature is kept unchanged, it is normally a controlled variable or background condition. It would become independent only if the experimenter intentionally used different temperatures and measured the resulting response. Thus A is the precise correction.

Correct answer: A. मापन की संगतता

Using a different procedure, instrument or criterion for each measurement makes the dependent-variable results difficult to compare. This mainly reduces consistency, also called reliability of the measurement procedure. The independent-variable range has not necessarily changed, and the control-group size and variable name are unrelated to this problem. Repeating one clearly defined method improves a fair comparison between trials.

Correct answer: B. स्वतंत्र चर बदला जाता है, आश्रित चर मापा जाता है और अन्य प्रभावकारी चर स्थिर रखे जाते हैं

A fair experiment changes one selected factor, the independent variable, and measures the response, the dependent variable. Other factors that could influence the response are controlled by keeping them constant. This arrangement helps establish a meaningful relationship between cause and effect. Option A reverses the roles, while C changes too many factors and D ignores the measured response.

Correct answer: A. प्रारंभिक जल-द्रव्यमान समान रखना

The amount of water initially present directly affects how long a cloth takes to dry. If it differs between pieces, the result may be caused by water mass rather than fan speed. Therefore the initial water mass should be measured and made equal, while fan speed remains the independent variable and drying time remains the dependent variable. Option B would prevent the intended comparison.

Correct answer: B. स्प्रिंग का प्रकार

Different springs may have different stiffnesses, thicknesses or materials, so the same load can produce different extensions. Because a new spring is used in each trial, spring type has not been controlled. The applied load is the independent variable, and the increase in length is the dependent measurement. Using one identical spring, or matched springs, would make the comparison fairer.