Why isn't my code changing values each trial?

Question

My code is supposed to take command line arguments argv[1]: trials argv[2]: samples argv[3]: minimum val argv[4]: max val

I wrote a loop from 0 to argv[1] to get the number of trials specified. However, the data does not change for each trial.

int main(int argc, char *argv[])
{
        for (int i = 1; i < argc; i ++)
        {
                if (is_valid_int(argv[i]) == 1)
                {
                        continue;
                }
                else
                {
                        printf("%s is not a valid integer\n", argv[i]);

                }
        }
        for (int k = 0; k < atoi(argv[1]); k++)
        {
                int size = atoi(argv[2]);
                int lower = atoi(argv[3]);
                int upper = atoi(argv[4]);
                int *min = NULL;
                int *max = NULL;
                double *mean = NULL;
                double *stddev = NULL;

           
                int *result = generate_population(size, lower, upper);
                get_stats(result, size, min, max, mean, stddev);
        }
        return 0;
}
void get_stats(int *a, int size, int *min, int *max, double *mean, double *stddev)
{

        min = &a[0];
        max = &a[0];
        double tempMean = 0;
        for (int i = 0; i < size; i ++)
        {
                printf("%d\n", a[i]);
                tempMean = tempMean + a[i];
        }
        tempMean = tempMean / size;
        mean = &tempMean;
        printf("mean: %g\n", *mean);

        double sumSquared = 0;
        for (int l = 0; l < size; l++)
        {
                sumSquared = sumSquared + ((a[l] - *mean)*(a[l] - *mean));
        }
        double tempStandardDev = sqrt((sumSquared/size));
        stddev = &tempStandardDev;
        printf("standard Dev: %g\n", *stddev);



        for (int j = 0; j < size; j++)
        {
                if (a[j] < *min)
                {
                        min = &a[j];
                }
        }
        printf("Minimum: %d\n", *min);
        for (int k = 0; k < size; k++)
        {
                if (a[k] > *max)
                {
                        max = &a[k];
                }
        }
        printf("max: %d\n", *max);
        free(a);

}
int *generate_population(int size, int lower, int upper)
{
        int *my_array=(int*)malloc(size * sizeof(int));
        srand(time(NULL));
        for (int i = 0; i < size; i++)
        {
                my_array[i] = (rand() % (upper - lower + 1)) + lower;
        }

        return my_array;
}

Is my srand() in the wrong location? I am also suspecting im incorrectly using pointers which is causing me not to change the value after each trial.