The comparison of a measurement with a known standard, used to determine whether the measurement is reliable. Measurement accuracy is identified as the difference between the measurement of a factor and the accepted value for that factor from a trusted external source, or the percentage by which the two values differ.
Here the question is stating about the hot deserts.
Hot deserts are characterized by extremely hot and arid climate.
Average annual range of rainfall is as low as 25 cm.
Deserts lack vegetation except at some patches.
Plants that survive in hot deserts have several adaptation to check the loss of water through transpiration.
These adaptation include, succulent stems, cuticularized epidermis, Reduction of leaves into spines or thorns, stems modified into phylloclades and deep roots to absorb water.
She could use a control to compare her data to and make sure it is cleaner. Ex. Use the old detergent on ten shirts and then use the new detergent on another ten shirts. She would then compare the shirts she did each detergent on and come up with her conclusion.