What kind of scientific investigations do not involve experiments?

Experimental investigations.

Explanation:

The process involves in experimental investigations  is a "fair test" is designed and manipulation of variables, measured and controlled to collect evidence to refuse or support  a formal relationship.

Experimental investigations posses a control group which does not need or receive any kind of experimental  treatment.

For example, a student might conduct an investigation  " Discuss the effect of light color on the growth of plants?" the student altered the variable color of light in this experiment . The student may compare green light to natural light to red light.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.

radiation

explanation:

heat is transmitted by radiation